Drug Dosage Calculator Online

Drug Dosage Calculator

kg lbs

mg/kg

mg/mL

function calculateDosage() { var patientWeight = parseFloat(document.getElementById("patientWeight").value); var weightUnit = document.getElementById("weightUnit").value; var desiredDosePerKg = parseFloat(document.getElementById("desiredDosePerKg").value); var drugConcentration = parseFloat(document.getElementById("drugConcentration").value); // Input validation if (isNaN(patientWeight) || patientWeight <= 0) { document.getElementById("result").innerHTML = "Please enter a valid positive Patient Weight."; return; } if (isNaN(desiredDosePerKg) || desiredDosePerKg <= 0) { document.getElementById("result").innerHTML = "Please enter a valid positive Desired Dose."; return; } if (isNaN(drugConcentration) || drugConcentration <= 0) { document.getElementById("result").innerHTML = "Please enter a valid positive Drug Concentration."; return; } // Convert patient weight to kg if in lbs var patientWeightKg = patientWeight; if (weightUnit === "lbs") { patientWeightKg = patientWeight / 2.20462; // 1 kg = 2.20462 lbs } // Calculate total dose needed in mg var totalDoseMg = desiredDosePerKg * patientWeightKg; // Calculate volume to administer in mL var volumeToAdministerMl = totalDoseMg / drugConcentration; document.getElementById("result").innerHTML = "Volume to Administer: " + volumeToAdministerMl.toFixed(2) + " mL"; }

Understanding the Drug Dosage Calculator

Accurate drug dosage is paramount in healthcare to ensure patient safety and treatment efficacy. Administering too little medication can render it ineffective, while too much can lead to severe adverse effects or toxicity. This online Drug Dosage Calculator is designed to assist healthcare professionals and students in quickly determining the correct volume of a liquid medication to administer based on a patient's weight, the desired dose per kilogram, and the drug's concentration.

How Drug Dosage is Calculated

The core principle behind calculating drug dosage involves determining the total amount of medication (in milligrams, micrograms, or units) a patient needs, and then converting that into the volume (in milliliters) of the available drug solution. The formula used by this calculator is:

Volume to Administer (mL) = (Desired Dose (mg/kg) × Patient Weight (kg)) / Drug Concentration (mg/mL)

Let's break down the inputs:

Patient Weight

The patient's weight is a critical factor, especially in pediatrics and for many weight-based medications. It's essential to use an accurate and current weight. The calculator allows you to input weight in kilograms (kg) or pounds (lbs), automatically converting lbs to kg for the calculation.

Desired Dose (per kg of body weight)

This refers to the prescribed amount of medication per unit of body weight, typically expressed as milligrams per kilogram (mg/kg), micrograms per kilogram (mcg/kg), or units per kilogram (units/kg). This value is usually found in drug monographs, physician orders, or institutional guidelines.

Drug Concentration (as supplied)

Drug concentration indicates how much active medication is present in a given volume of solution. It's commonly expressed as milligrams per milliliter (mg/mL), micrograms per milliliter (mcg/mL), or units per milliliter (units/mL). This information is always available on the drug's packaging or vial.

Using the Calculator: Step-by-Step

1. Enter Patient Weight: Input the patient's weight and select the correct unit (kg or lbs).
2. Enter Desired Dose: Input the prescribed dose per kilogram (e.g., 5 mg/kg).
3. Enter Drug Concentration: Input the concentration of the drug solution you have (e.g., 20 mg/mL).
4. Click "Calculate Dosage": The calculator will instantly display the exact volume in milliliters (mL) to administer.

Realistic Examples

Example 1: Adult Patient

• Patient Weight: 70 kg
• Desired Dose: 5 mg/kg
• Drug Concentration: 100 mg in 5 mL (which is 20 mg/mL)
• Calculation: (5 mg/kg × 70 kg) / 20 mg/mL = 350 mg / 20 mg/mL = 17.5 mL

Example 2: Pediatric Patient (Weight in lbs)

• Patient Weight: 25 lbs
• Desired Dose: 10 mg/kg
• Drug Concentration: 250 mg in 10 mL (which is 25 mg/mL)
• Conversion: 25 lbs ÷ 2.20462 lbs/kg ≈ 11.34 kg
• Calculation: (10 mg/kg × 11.34 kg) / 25 mg/mL = 113.4 mg / 25 mg/mL = 4.54 mL (rounded to two decimal places)

Example 3: Different Concentration

• Patient Weight: 60 kg
• Desired Dose: 2 mg/kg
• Drug Concentration: 50 mg in 2 mL (which is 25 mg/mL)
• Calculation: (2 mg/kg × 60 kg) / 25 mg/mL = 120 mg / 25 mg/mL = 4.8 mL

Important Considerations & Disclaimer

This Drug Dosage Calculator is provided for educational and informational purposes only and should NOT be used for actual patient care. It is a supplementary tool and does not replace the critical judgment, knowledge, and responsibility of a qualified healthcare professional.

• Always Verify: Double-check all calculations with a second healthcare professional or an official drug reference.
• Patient-Specific Factors: Dosage may need adjustment based on individual patient factors such as age, renal or hepatic function, comorbidities, and concurrent medications.
• Drug Monographs: Always refer to the official drug monograph, package insert, or institutional guidelines for complete and accurate dosing information, contraindications, and administration instructions.
• Units: Pay close attention to units (mg, mcg, units, kg, lbs, mL) to prevent medication errors.
• Emergency Situations: In emergency situations, follow established protocols and seek immediate medical advice.

By using this calculator, you acknowledge and agree that you are responsible for verifying all calculations and that this tool is not a substitute for professional medical advice or clinical judgment.