Kilograms (kg)
Pounds (lb)
Select the unit for patient weight.
Enter the prescribed dose per kilogram or pound (e.g., 5 mg/kg).
Milligrams (mg)
Micrograms (mcg)
Milliliters (mL)
Units
Select the unit for the final dose.
If calculating volume, enter concentration (e.g., 250 mg/mL). Leave blank if not applicable.
N/A
mg/mL
mcg/mL
mg/g
units/mL
Select the unit for concentration.
Calculation Results
—
— Weight (kg)
— Calculated Dose
— Volume to Administer
Formula Used:
1. Convert weight to kilograms if necessary.
2. Total Dose = Patient Weight (kg) * Dose Per Unit Weight.
3. Volume = Total Dose / Concentration (if applicable).
Standard Dose Ranges (Example)
Medication Class
Typical Dose Range (mg/kg/day)
Unit
Antibiotics (e.g., Amoxicillin)
20 – 40
mg/kg/day
Analgesics (e.g., Paracetamol)
10 – 15
mg/kg/dose
Antipyretics (e.g., Ibuprofen)
5 – 10
mg/kg/dose
Chemotherapy Agents (Varies Widely)
Highly Variable
mg/m² or mg/kg
Vitamins (e.g., Vitamin D)
Variable (IU/kg)
IU/kg
Note: These are general ranges and may vary significantly based on specific medication, indication, patient condition, and physician orders. Always refer to the official drug monograph.
Dose vs. Weight Relationship
Visualizing how the calculated total dose changes with patient weight, assuming a constant dose per kilogram and concentration.
Understanding Dose Calculation by Weight
What is Dose Calculation by Weight?
Dose calculation by weight is a fundamental principle in pharmacology and medicine used to determine the appropriate amount of a medication or treatment to administer to a patient based on their body mass. This method ensures that the therapeutic effect is achieved while minimizing the risk of toxicity, as different individuals, especially children and adults, can have vastly different metabolic rates and drug distribution volumes influenced by their size. Essentially, it's about tailoring the medicine to the patient's scale.
Who should use it: Healthcare professionals, including doctors, nurses, pharmacists, and veterinarians, routinely use dose calculation by weight. It is particularly critical in pediatric care, critical care units, oncology, and anesthesia where precise dosing is paramount. Patients receiving certain complex or potent medications might also be advised to understand this calculation.
Common misconceptions: A common misconception is that all medications are dosed solely by weight. In reality, age, organ function (liver, kidney), specific medical conditions, and drug interactions also play significant roles. Another is that weight-based dosing applies equally across all drugs; however, many medications have standard adult doses regardless of weight for simplicity, especially if the therapeutic window is wide. It's also sometimes misunderstood that "more weight equals more drug" without considering drug half-life and saturation points.
Dose Calculation by Weight Formula and Mathematical Explanation
The core principle involves establishing a relationship between the desired therapeutic effect and the patient's mass. The most common formula for dose calculation by weight is:
Total Dose = Patient Weight × Prescribed Dose Per Unit Weight
This formula allows for a direct calculation of the total quantity of the active pharmaceutical ingredient (API) needed for a single administration or a daily total, depending on how the "Prescribed Dose Per Unit Weight" is defined.
For medications that are supplied in a liquid form (like many pediatric medications or intravenous infusions), an additional step is often required to determine the volume to administer:
Volume to Administer = Total Dose / Medication Concentration
Variable Explanations:
Variable
Meaning
Unit
Typical Range
Patient Weight
The measured body mass of the individual receiving the medication.
Kilograms (kg) or Pounds (lb)
0.1 kg (premature infant) to over 200 kg (obese adult)
Prescribed Dose Per Unit Weight
The standard therapeutic dose recommended per unit of body mass (e.g., mg per kg, mcg per lb). This is often found in drug formularies or clinical guidelines.
e.g., mg/kg, mcg/lb, mL/kg, Units/kg
Varies widely by drug; e.g., 0.01 mg/kg for some potent drugs to 50 mg/kg for others.
Total Dose
The calculated total amount of the active drug substance required for the patient.
e.g., mg, mcg, mL, Units
Dependent on weight and dose rate; can range from micrograms to grams.
Medication Concentration
The amount of active drug present in a given volume or mass of the pharmaceutical product (e.g., how potent the solution is).
The final volume of the liquid medication that needs to be measured and given to the patient to achieve the calculated total dose.
e.g., mL, L
Typically mL for injections/oral liquids; may be L for IV fluids.
Practical Examples (Real-World Use Cases)
Let's explore some scenarios where dose calculation by weight is applied:
Example 1: Pediatric Pain Management
A 3-year-old child weighing 15 kg needs Paracetamol (Acetaminophen) for fever. The standard pediatric dose for Paracetamol is 10-15 mg/kg/dose. The available Paracetamol syrup has a concentration of 120 mg per 5 mL.
Patient Weight: 15 kg
Dose Per Unit Weight: Let's use the higher end for calculation: 15 mg/kg
Dose Unit: mg
Concentration: 120 mg/5 mL (This implies 24 mg/mL, but we'll use the ratio form for clarity in calculation)
Calculation:
Total Dose: 15 kg × 15 mg/kg = 225 mg
Volume to Administer: (225 mg / 120 mg) × 5 mL = 1.875 × 5 mL = 9.375 mL
Interpretation: The child should receive approximately 9.4 mL of the Paracetamol syrup to achieve a dose of 225 mg. This ensures the child gets an appropriate amount of medication based on their size.
Example 2: Antibiotic Administration in Adults
An adult patient weighing 60 kg requires an antibiotic, Levofloxacin, at a dose of 7.5 mg/kg. The available formulation is a 250 mg tablet.
Patient Weight: 60 kg
Dose Per Unit Weight: 7.5 mg/kg
Dose Unit: mg
Concentration: N/A (using solid dosage form)
Calculation:
Total Dose: 60 kg × 7.5 mg/kg = 450 mg
Interpretation: The patient needs 450 mg of Levofloxacin. Since the tablets are 250 mg, the prescriber might order one 250 mg tablet plus another partial tablet, or adjust the dose slightly based on available formulations and clinical judgment. This calculation highlights the required total dose.
How to Use This Dose Calculation by Weight Calculator
Our calculator simplifies the process of determining medication dosages based on patient weight. Follow these steps for accurate results:
Enter Patient Weight: Input the patient's current body weight in the 'Patient Weight' field.
Select Weight Unit: Choose the correct unit (Kilograms or Pounds) from the 'Weight Unit' dropdown. If your weight is in pounds, the calculator will automatically convert it to kilograms for internal calculations, as most medical dosages are standardized per kg.
Input Dose Per Unit Weight: Enter the prescribed dosage rate specified by the healthcare provider or drug guidelines (e.g., if the order is "5 mg per kg", enter '5').
Select Dose Unit: Choose the unit for the prescribed dose (e.g., mg, mcg, mL, Units). This determines the unit for the 'Calculated Dose Amount'.
Enter Concentration (Optional): If you are administering a liquid medication and need to determine the volume, enter the medication's concentration (e.g., '250' for 250 mg per mL). Select the corresponding 'Concentration Unit' from the dropdown. If you are administering solid dosage forms (like tablets) or if volume is not relevant, leave these fields blank or select 'N/A'.
Click 'Calculate Dose': The calculator will instantly display the results.
How to read results:
Primary Highlighted Result: This shows the calculated 'Total Dose' required in the selected 'Dose Unit'.
Weight (kg): Displays the patient's weight converted to kilograms.
Calculated Dose Amount: Shows the total amount of the active drug substance needed. This is the primary output.
Volume to Administer: If concentration was provided, this shows the volume (in mL, typically) of the liquid medication that contains the calculated 'Calculated Dose Amount'.
Decision-making guidance: Always cross-reference the calculated dose with standard drug reference materials and physician's orders. This calculator is a tool to aid professionals and should not replace clinical judgment. If the calculated volume seems unusually large or small, double-check all inputs and consult a senior clinician or pharmacist.
Key Factors That Affect Dose Calculation by Weight Results
While weight is a primary determinant, several other factors can modify the final dosage or its effectiveness:
Age: Pediatric and geriatric patients have different pharmacokinetic profiles. Infants may have immature liver and kidney function, affecting drug metabolism and excretion, while the elderly may have reduced organ function and altered body composition (e.g., increased fat, decreased water). This is why pediatric dosing often relies heavily on weight-based calculations but with specific pediatric considerations.
Organ Function (Renal and Hepatic): The kidneys excrete many drugs, and the liver metabolizes them. Impaired function in these organs can lead to drug accumulation and toxicity, often requiring dose reduction even if the weight-based calculation suggests a standard dose.
Body Composition (Lean Body Mass vs. Fat Mass): Some drugs distribute primarily into lean tissues, while others distribute into fatty tissues. Dosing based solely on total body weight might be inaccurate for obese patients if the drug primarily acts on lean mass. In such cases, ideal body weight or adjusted body weight might be used.
Severity of Condition: For severe infections or critical illnesses, higher doses might be required to achieve therapeutic concentrations, sometimes exceeding standard weight-based recommendations, under strict clinical supervision.
Drug Interactions: Concurrent administration of other medications can alter the metabolism or excretion of the drug in question, potentially requiring dose adjustments. For instance, some drugs inhibit enzymes that metabolize another drug, leading to higher levels.
Therapeutic Drug Monitoring (TDM): For certain drugs with a narrow therapeutic index (e.g., digoxin, certain antibiotics like vancomycin, antiepileptics), blood levels are monitored. The initial dose calculated by weight serves as a starting point, but subsequent doses are adjusted based on measured drug concentrations in the blood.
Route of Administration: The bioavailability of a drug can differ depending on whether it's given orally, intravenously, intramuscularly, etc. IV doses are often lower than oral doses because they bypass first-pass metabolism in the liver.
Frequently Asked Questions (FAQ)
Is dose calculation by weight only for children?
Most often emphasized for children due to their rapidly changing physiology and smaller size, but it is also used for adults, especially for potent medications, chemotherapy, anesthesia, and in critical care settings where precise dosing is crucial. Many adult drug labels will still provide dosing guidelines per kilogram.
What is the difference between mg/kg and mg/m² dosing?
mg/kg refers to milligrams of drug per kilogram of body weight. mg/m² refers to milligrams of drug per square meter of body surface area. Body surface area (BSA) is often used in chemotherapy because drug distribution and cell turnover are thought to correlate more closely with BSA than just weight, especially in adults and children of different body compositions.
What happens if I give the wrong dose?
Giving too low a dose may result in treatment failure (e.g., infection not clearing, pain not managed). Giving too high a dose can lead to toxicity, adverse effects, and organ damage. It's crucial to be accurate.
Do I always need to convert pounds to kilograms?
Yes, for medical calculations, it's standard practice to use kilograms. Most drug dosing guidelines are provided in mg/kg or mcg/kg. If a patient's weight is given in pounds, you must convert it (1 lb ≈ 0.453592 kg). Our calculator handles this conversion automatically.
What if the calculated volume is very large (e.g., > 10 mL for an injection)?
This might indicate an error in input, a highly dilute concentration, or a medication that requires a large volume. Double-check your inputs. For very large volumes, alternative routes of administration or different concentrations might be considered, and consultation with a pharmacist is recommended.
How do I calculate a daily dose from a per-dose calculation?
If the "Dose Per Unit Weight" is given as, for example, "15 mg/kg/dose" and the patient needs the medication 4 times a day (q6h), you would first calculate the single dose (e.g., 15 mg/kg * 50 kg = 750 mg/dose). Then, multiply the single dose by the number of doses per day (750 mg/dose * 4 doses/day = 3000 mg/day). Always refer to the prescriber's intended frequency.
Can I use this calculator for veterinary doses?
The principles are the same, but specific drug dosages and ranges for animals differ significantly from humans. Always use veterinary-specific formularies and calculators when dosing animals.
What does "rounding" mean in dose calculation?
Often, calculated doses or volumes need to be rounded to the nearest practical unit for administration (e.g., nearest mL for liquids, nearest quarter-tablet for pills). However, rounding rules can vary, and for potent drugs, rounding might be to the nearest 0.1 unit. Always follow specific protocols or prescriber instructions.
Drug Interaction CheckerExplore potential interactions between different medications to ensure safe co-administration.
Body Surface Area (BSA) CalculatorCalculate Body Surface Area, often used for chemotherapy dosing, which is another method of patient-specific calculation.
Pediatric Dosing GuidelinesAccess a curated list of common pediatric medication dosing recommendations and considerations.
Renal Function EstimatorEstimate kidney function (e.g., eGFR) which is crucial for adjusting doses of renally excreted drugs.
Pharmacokinetics 101Learn the fundamentals of how the body processes drugs (Absorption, Distribution, Metabolism, Excretion) to understand dosing principles better.
// Global variables for calculator state
var originalPatientWeight = 70;
var originalWeightUnit = 'kg';
var originalDosePerWeight = 10;
var originalDoseUnit = 'mg';
var originalConcentration = 250;
var originalConcentrationUnit = 'mg/mL';
function convertWeightToKg(weight, unit) {
if (unit === 'lb') {
return weight * 0.453592;
}
return weight;
}
function convertConcentrationToMgMl(concentration, unit) {
if (unit === 'mcg/mL') {
return concentration / 1000;
} else if (unit === 'mg/g') {
// Assuming density of 1 g/mL for simplicity in medical context for solids/semi-solids if appropriate
// In reality, this would depend on the specific formulation. For mg/mL is more common for liquids.
// If it's a solid tablet/powder, concentration calculation for volume is not applicable this way.
// Let's assume mg/g implies mg per mL for calculation purposes here for liquid-like suspensions.
// A more robust solution might distinguish solid vs liquid concentration units.
// For this calculator, let's prioritize mg/mL, mcg/mL. mg/g might be less direct for volume calc.
// For now, if mg/g is entered, we'll treat it as mg/mL, acknowledging this simplification.
return concentration;
} else if (unit === 'units/mL') {
// This requires a conversion factor from Units to mg if the dose unit is mg.
// For simplicity here, if dose unit is 'units', we calculate volume based on units/mL.
// If dose unit is 'mg' and concentration is 'units/mL', it's an incompatible input unless a conversion factor is provided.
// Let's assume if doseUnit is 'units', then concentrationUnit should be 'units/mL'.
// If doseUnit is 'mg' and concentrationUnit is 'units/mL', we can't calculate volume directly without a mg/unit conversion.
// To avoid NaN, we'll return NaN or handle it. Let's return NaN if units mismatch.
return NaN; // Indicate incompatible units for calculation
}
return concentration; // Assume mg/mL or already compatible
}
function calculateDose() {
var patientWeightInput = document.getElementById("patientWeight");
var weightUnitSelect = document.getElementById("weightUnit");
var dosePerWeightInput = document.getElementById("dosePerWeight");
var doseUnitSelect = document.getElementById("doseUnit");
var concentrationInput = document.getElementById("concentration");
var concentrationUnitSelect = document.getElementById("concentrationUnit");
// Error message elements
var patientWeightError = document.getElementById("patientWeightError");
var dosePerWeightError = document.getElementById("dosePerWeightError");
var concentrationError = document.getElementById("concentrationError");
var concentrationUnitError = document.getElementById("concentrationUnitError");
// Reset error messages
patientWeightError.textContent = "";
dosePerWeightError.textContent = "";
concentrationError.textContent = "";
concentrationUnitError.textContent = "";
// Get input values
var patientWeight = parseFloat(patientWeightInput.value);
var weightUnit = weightUnitSelect.value;
var dosePerWeight = parseFloat(dosePerWeightInput.value);
var doseUnit = doseUnitSelect.value;
var concentration = parseFloat(concentrationInput.value);
var concentrationUnit = concentrationUnitSelect.value;
var isValid = true;
// Input validation
if (isNaN(patientWeight) || patientWeight <= 0) {
patientWeightError.textContent = "Please enter a valid patient weight greater than zero.";
isValid = false;
}
if (isNaN(dosePerWeight) || dosePerWeight <= 0) {
dosePerWeightError.textContent = "Please enter a valid dose per unit weight greater than zero.";
isValid = false;
}
var concentrationValid = true;
if (concentrationInput.value !== "") {
if (isNaN(concentration) || concentration <= 0) {
concentrationError.textContent = "Please enter a valid concentration greater than zero.";
concentrationValid = false;
isValid = false;
}
if (concentrationUnit === "") {
concentrationUnitError.textContent = "Please select a concentration unit if providing concentration.";
concentrationValid = false;
isValid = false;
}
} else {
concentrationValid = true; // Concentration is optional, so it's valid if empty
}
if (!isValid) {
// Clear results if invalid input
document.getElementById("primaryResult").textContent = "–";
document.getElementById("weightInKg").querySelector('span').textContent = "–";
document.getElementById("calculatedDoseAmount").querySelector('span').textContent = "–";
document.getElementById("volumeToAdminister").querySelector('span').textContent = "–";
return;
}
// Calculations
var weightInKg = convertWeightToKg(patientWeight, weightUnit);
var calculatedDoseAmount = patientWeight * dosePerWeight; // This calculation uses the ORIGINAL units provided by user
var volumeToAdminister = "–"; // Default value
// Handle dose unit conversion if necessary for intermediate display clarity
var displayDoseUnit = doseUnit;
var displayCalculatedDoseAmount = calculatedDoseAmount;
// Logic for volume calculation
if (concentrationInput.value !== "" && concentrationValid) {
var effectiveConcentrationMgMl = convertConcentrationToMgMl(concentration, concentrationUnit);
// Check for incompatible units specifically for volume calculation
if (isNaN(effectiveConcentrationMgMl) && doseUnit === 'mg' && concentrationUnit === 'units/mL') {
concentrationError.textContent = "Cannot calculate volume: Dose unit (mg) is incompatible with concentration unit (units/mL).";
isValid = false;
} else if (isNaN(effectiveConcentrationMgMl) && doseUnit === 'units' && concentrationUnit === 'mg/mL') {
concentrationError.textContent = "Cannot calculate volume: Dose unit (units) is incompatible with concentration unit (mg/mL).";
isValid = false;
} else if (isNaN(effectiveConcentrationMgMl)) {
concentrationError.textContent = "Invalid concentration unit for volume calculation.";
isValid = false;
}
if (isValid) {
// Perform volume calculation. Ensure units are compatible.
// If doseUnit is 'mg' and concentrationUnit is 'mg/mL', then Volume = mg / (mg/mL) = mL. Correct.
// If doseUnit is 'units' and concentrationUnit is 'units/mL', then Volume = units / (units/mL) = mL. Correct.
// We need to ensure the numeric values align.
// For simplicity, if concentration was successfully converted to a usable number, proceed.
if (doseUnit === 'mg' && concentrationUnit === 'mg/mL') {
volumeToAdminister = calculatedDoseAmount / effectiveConcentrationMgMl;
} else if (doseUnit === 'mcg' && concentrationUnit === 'mcg/mL') {
volumeToAdminister = calculatedDoseAmount / effectiveConcentrationMgMl;
} else if (doseUnit === 'mL' && concentrationUnit === 'mg/mL') { // If dose is already in mL, and concentration is mg/mL, this implies a different calculation or error.
// This scenario is unusual. If dose is requested in mL, and concentration is mg/mL, it typically means we need X mg, and concentration tells us mg/mL.
// The calculation should still be: Target Dose (mg) / Concentration (mg/mL) = Volume (mL).
// If doseUnit is mL, it implies the desired output is volume, not mass.
// Re-evaluate: If Dose Unit is mL, it means the user expects the final output for 'Calculated Dose Amount' to be in mL. This is rare unless the drug is dosed by volume directly.
// Let's assume Dose Unit refers to the active ingredient. So, if doseUnit is 'mL', it might be a mistake.
// For robustness, we can try to interpret: if doseUnit is mL, it means we want X mL of liquid, BUT the dosePerWeight is likely still mg/kg or similar.
// This implies a mismatch. Let's stick to standard: Dose Unit = active ingredient unit.
// So, if doseUnit is 'mg', concentration 'mg/mL', volume is calculated.
// If doseUnit is 'units', concentration 'units/mL', volume is calculated.
// If doseUnit is 'mL', it's likely an error in interpretation or input.
// Let's ensure the doseUnit and concentrationUnit are compatible for volume calculation.
// E.g. doseUnit=mg, concentrationUnit=mcg/mL needs conversion.
// For simplicity, we'll focus on direct matches or explicit conversions.
// Our convertConcentrationToMgMl already tries to normalize.
// If doseUnit is 'mg' and concentrationUnit is 'mcg/mL', we need to convert mcg/mL to mg/mL.
// If doseUnit is 'mcg' and concentrationUnit is 'mg/mL', we need to convert mg/mL to mcg/mL.
// Refined volume calculation logic:
var targetDose = calculatedDoseAmount; // in the specified doseUnit
var concValue = concentration;
var concUnit = concentrationUnit;
// Normalize dose and concentration to common units if possible for calculation
var normalizedTargetDose = targetDose;
var normalizedConcValue = concValue;
var normalizedDoseUnit = doseUnit;
var normalizedConcUnit = concUnit;
// Try to convert dose to mg if it's mcg, assuming concentration is mg/mL or mcg/mL
if (doseUnit === 'mcg' && (concentrationUnit === 'mg/mL' || concentrationUnit === 'mcg/mL')) {
normalizedTargetDose = targetDose / 1000; // mcg to mg
normalizedDoseUnit = 'mg';
}
// Try to convert dose to units if it's something else, assuming concentration is units/mL
if (doseUnit === 'units' && concentrationUnit === 'units/mL') {
// Already compatible in terms of units type
}
// Convert concentration to mg/mL if it's mcg/mL
if (concentrationUnit === 'mcg/mL') {
normalizedConcValue = concValue / 1000;
normalizedConcUnit = 'mg/mL';
}
// Convert concentration to units/mL if it's something else and dose is units
if (concentrationUnit === 'units/mL' && doseUnit === 'units') {
// Compatible
}
// Final check on compatible unit types for volume calculation
var canCalculateVolume = false;
if (normalizedDoseUnit === 'mg' && normalizedConcUnit === 'mg/mL') {
canCalculateVolume = true;
} else if (normalizedDoseUnit === 'mcg' && normalizedConcUnit === 'mcg/mL') {
canCalculateVolume = true;
} else if (normalizedDoseUnit === 'units' && normalizedConcUnit === 'units/mL') {
canCalculateVolume = true;
} else if (normalizedDoseUnit === 'mL') {
// This case is tricky. If the desired dose unit *is* mL, it implies the target output is already volume.
// However, the dosePerWeight is usually mass-based.
// Let's assume if doseUnit is mL, it's an error or implies a different calculation model not supported here.
// We'll prevent calculation if doseUnit is mL directly.
concentrationError.textContent = "Dose unit 'mL' is not typically used with 'Dose Per Unit Weight'. Use mass units (mg, mcg).";
isValid = false;
}
if (canCalculateVolume) {
volumeToAdminister = normalizedTargetDose / normalizedConcValue;
// Round volume to a reasonable number of decimal places for practical use
volumeToAdminister = parseFloat(volumeToAdminister.toFixed(2)); // e.g., 2 decimal places
} else if (concentrationInput.value !== "") {
// If concentration was provided but units are incompatible for calculation
concentrationError.textContent = "Incompatible units for volume calculation. Ensure Dose Unit and Concentration Unit align (e.g., mg with mg/mL, units with units/mL).";
isValid = false;
}
}
}
// Display Results
var primaryResultSpan = document.getElementById("primaryResult");
var weightInKgSpan = document.getElementById("weightInKg").querySelector('span');
var calculatedDoseAmountSpan = document.getElementById("calculatedDoseAmount").querySelector('span');
var volumeToAdministerSpan = document.getElementById("volumeToAdminister").querySelector('span');
if (isValid) {
primaryResultSpan.textContent = displayCalculatedDoseAmount.toFixed(2) + " " + displayDoseUnit; // Primary result is the calculated dose amount
weightInKgSpan.textContent = weightInKg.toFixed(2);
calculatedDoseAmountSpan.textContent = displayCalculatedDoseAmount.toFixed(2) + " " + displayDoseUnit;
if (volumeToAdminister !== "–") {
volumeToAdministerSpan.textContent = volumeToAdminister + " mL"; // Assume mL for volume output
} else {
volumeToAdministerSpan.textContent = "–";
}
} else {
// Clear results if any validation failed
primaryResultSpan.textContent = "–";
weightInKgSpan.textContent = "–";
calculatedDoseAmountSpan.textContent = "–";
volumeToAdministerSpan.textContent = "–";
}
// Update chart
updateChart(patientWeight, weightUnit, dosePerWeight, doseUnit);
}
function resetCalculator() {
document.getElementById("patientWeight").value = originalPatientWeight;
document.getElementById("weightUnit").value = originalWeightUnit;
document.getElementById("dosePerWeight").value = originalDosePerWeight;
document.getElementById("doseUnit").value = originalDoseUnit;
document.getElementById("concentration").value = originalConcentration;
document.getElementById("concentrationUnit").value = originalConcentrationUnit;
// Clear error messages
document.getElementById("patientWeightError").textContent = "";
document.getElementById("dosePerWeightError").textContent = "";
document.getElementById("concentrationError").textContent = "";
document.getElementById("concentrationUnitError").textContent = "";
// Recalculate and update results display
calculateDose();
}
function copyResults() {
var primaryResult = document.getElementById("primaryResult").textContent;
var weightInKg = document.getElementById("weightInKg").querySelector('span').textContent;
var calculatedDoseAmount = document.getElementById("calculatedDoseAmount").querySelector('span').textContent;
var volumeToAdminister = document.getElementById("volumeToAdminister").textContent;
var assumptions = [
"Patient Weight: " + document.getElementById("patientWeight").value + " " + document.getElementById("weightUnit").value,
"Dose Per Unit Weight: " + document.getElementById("dosePerWeight").value + " " + document.getElementById("doseUnit").value + " per " + (document.getElementById("weightUnit").value === 'kg' ? 'kg' : 'lb'),
"Medication Concentration: " + (document.getElementById("concentration").value ? document.getElementById("concentration").value + " " + document.getElementById("concentrationUnit").value : "N/A")
];
var copyText = "— Dose Calculation Results —\n\n";
copyText += "Primary Result (Calculated Dose): " + primaryResult + "\n";
copyText += "Weight (kg): " + weightInKg + "\n";
copyText += "Calculated Dose Amount: " + calculatedDoseAmount + "\n";
copyText += "Volume to Administer: " + volumeToAdminister + "\n\n";
copyText += "— Key Assumptions —\n";
assumptions.forEach(function(item) {
copyText += "- " + item + "\n";
});
try {
navigator.clipboard.writeText(copyText).then(function() {
alert("Results copied to clipboard!");
}).catch(function(err) {
console.error("Failed to copy: ", err);
alert("Failed to copy results. Please copy manually.");
});
} catch (e) {
console.error("Clipboard API not available: ", e);
alert("Clipboard API not available. Please copy manually.");
}
}
// Charting Logic
var doseChart; // Declare chart variable globally
function updateChart(patientWeight, weightUnit, dosePerWeight, doseUnit) {
var ctx = document.getElementById('doseChart').getContext('2d');
// Clear previous chart if it exists
if (doseChart) {
doseChart.destroy();
}
// Generate data for the chart
var weights = [];
var calculatedDoses = [];
var volumes = []; // Add volume data series
var weightInKg = convertWeightToKg(patientWeight, weightUnit);
var minWeight = Math.max(1, weightInKg – 20); // Start slightly below current weight
var maxWeight = weightInKg + 40; // Go slightly above current weight
var step = (maxWeight – minWeight) / 10; // Number of data points
var concentration = parseFloat(document.getElementById("concentration").value);
var concentrationUnit = document.getElementById("concentrationUnit").value;
var hasConcentration = document.getElementById("concentration").value !== "";
for (var i = 0; i 0) {
var effectiveConcentrationMgMl = convertConcentrationToMgMl(concentration, concentrationUnit);
var currentVolume = "–";
// Basic check for unit compatibility for volume calculation
if (!isNaN(effectiveConcentrationMgMl) &&
((doseUnit === 'mg' && concentrationUnit === 'mg/mL') ||
(doseUnit === 'mcg' && concentrationUnit === 'mcg/mL') ||
(doseUnit === 'units' && concentrationUnit === 'units/mL'))
)
{
currentVolume = currentDose / effectiveConcentrationMgMl;
}
volumes.push(currentVolume === "–" ? 0 : currentVolume); // Use 0 if volume can't be calculated for this series
} else {
volumes.push(0); // No volume series if no concentration provided
}
}
// Chart configuration
doseChart = new Chart(ctx, {
type: 'line',
data: {
labels: weights, // X-axis labels (Weight in kg)
datasets: [
{
label: 'Calculated Total Dose (' + doseUnit + ')',
data: calculatedDoses,
borderColor: 'rgb(0, 74, 153)', // Primary color
backgroundColor: 'rgba(0, 74, 153, 0.1)',
fill: false,
tension: 0.1
}
].concat(hasConcentration && concentration > 0 && volumes.some(v => v > 0) ? [{ // Conditionally add volume series
label: 'Volume to Administer (mL)',
data: volumes,
borderColor: 'rgb(40, 167, 69)', // Success color
backgroundColor: 'rgba(40, 167, 69, 0.1)',
fill: false,
tension: 0.1
}] : [])
},
options: {
responsive: true,
maintainAspectRatio: false,
scales: {
x: {
title: {
display: true,
text: 'Patient Weight (kg)'
}
},
y: {
title: {
display: true,
text: 'Dose Amount / Volume'
},
beginAtZero: true
}
},
plugins: {
tooltip: {
callbacks: {
label: function(context) {
var label = context.dataset.label || ";
if (label) {
label += ': ';
}
if (context.parsed.y !== null) {
label += context.parsed.y.toFixed(2); // Format numbers nicely
}
return label;
}
}
}
}
}
});
}
// Initial calculation and chart update on page load
document.addEventListener('DOMContentLoaded', function() {
resetCalculator(); // Sets default values and calculates
// Initial chart update with default values
var initialPatientWeight = parseFloat(document.getElementById("patientWeight").value);
var initialWeightUnit = document.getElementById("weightUnit").value;
var initialDosePerWeight = parseFloat(document.getElementById("dosePerWeight").value);
var initialDoseUnit = document.getElementById("doseUnit").value;
updateChart(initialPatientWeight, initialWeightUnit, initialDosePerWeight, initialDoseUnit);
});
// Re-calculate and update chart whenever an input changes
var inputFields = document.querySelectorAll('.loan-calc-container input, .loan-calc-container select');
inputFields.forEach(function(input) {
input.addEventListener('input', calculateDose);
input.addEventListener('change', calculateDose); // For select elements
});