U-500 Dosing Calculator

U-500 Insulin Dosing Calculator

U-500 regular human insulin is a highly concentrated insulin, five times more potent than standard U-100 insulin. It is prescribed for patients with severe insulin resistance who require large daily doses. Due to its high concentration, accurate dosing is critical to prevent dangerous over- or under-dosing. This calculator helps convert a prescribed total daily dose into the correct volume for administration using either a standard U-100 insulin syringe or a tuberculin (TB) syringe.

Disclaimer: This tool is for informational purposes only and should not replace professional medical advice. Always confirm dosing instructions with your healthcare provider or pharmacist before administering insulin. Incorrect dosing can lead to serious health complications.

function calculateDose() { var totalDailyDoseStr = document.getElementById("totalDailyDose").value; var dosesPerDayStr = document.getElementById("dosesPerDay").value; var resultDiv = document.getElementById("result"); var totalDailyDose = parseFloat(totalDailyDoseStr); var dosesPerDay = parseInt(dosesPerDayStr, 10); if (isNaN(totalDailyDose) || totalDailyDose <= 0 || isNaN(dosesPerDay) || dosesPerDay <= 0) { resultDiv.innerHTML = 'Please enter valid, positive numbers for both fields.'; resultDiv.style.backgroundColor = '#f2dede'; resultDiv.style.borderColor = '#ebccd1'; return; } var dosePerInjection = totalDailyDose / dosesPerDay; var volumeInU100Syringe = dosePerInjection / 5; var volumeInTbSyringe = dosePerInjection / 500; var resultHTML = '

Calculation Results:

'; resultHTML += 'Dose per Injection: ' + dosePerInjection.toFixed(0) + ' units of U-500 insulin.'; resultHTML += '

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Method 1: Using a U-100 Insulin Syringe

'; resultHTML += 'To administer ' + dosePerInjection.toFixed(0) + ' units, you must draw up to the ' + volumeInU100Syringe.toFixed(0) + ' unit mark on the U-100 syringe.'; resultHTML += '(Calculation: ' + dosePerInjection.toFixed(0) + ' units ÷ 5 = ' + volumeInU100Syringe.toFixed(0) + ' "units" on syringe)'; resultHTML += '

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Method 2: Using a Tuberculin (TB) Syringe

'; resultHTML += 'To administer ' + dosePerInjection.toFixed(0) + ' units, you must draw up ' + volumeInTbSyringe.toFixed(2) + ' mL in the TB syringe.'; resultHTML += '(Calculation: ' + dosePerInjection.toFixed(0) + ' units ÷ 500 units/mL = ' + volumeInTbSyringe.toFixed(2) + ' mL)'; resultHTML += '

'; resultDiv.innerHTML = resultHTML; resultDiv.style.backgroundColor = '#e9f5ff'; resultDiv.style.borderColor = '#b3d7f0'; }

Understanding U-500 Insulin Dosing

The primary source of confusion and error with U-500 insulin is its concentration. Standard insulin (U-100) contains 100 units of insulin per milliliter (mL). U-500 insulin contains 500 units per mL, making it five times as strong. When using a standard U-100 syringe, which is calibrated for U-100 insulin, a conversion is necessary. This is because the volume of U-500 insulin needed is one-fifth the volume of U-100 insulin for the same unit dose.

• U-100 Syringe Conversion: The actual unit dose must be divided by 5 to determine the correct marking on a U-100 syringe. For example, a prescribed 100-unit dose of U-500 insulin requires drawing the liquid up to the 20-unit mark on a U-100 syringe (100 ÷ 5 = 20).
• Tuberculin (TB) Syringe: A TB syringe is measured in milliliters (mL), which avoids the confusion of "units" on the syringe barrel. This is often considered the safer method. To calculate the volume in mL, divide the prescribed unit dose by 500 (the concentration of U-500 insulin). For example, a 100-unit dose requires 0.20 mL (100 ÷ 500 = 0.20).

Example Calculation

Let's walk through a common scenario:

• A patient is prescribed a Total Daily Dose of 240 units of U-500 insulin.
• This is to be administered in 3 separate doses throughout the day.

1. Calculate Dose per Injection: 240 total units / 3 doses = 80 units per injection.
2. Calculate for U-100 Syringe: 80 units / 5 = 16 unit mark. The patient would draw the U-500 insulin to the 16-unit line on the U-100 syringe.
3. Calculate for TB Syringe: 80 units / 500 units/mL = 0.16 mL. The patient would draw 0.16 mL into the TB syringe.

Critical Safety Information

Due to the high risk of error, many healthcare systems recommend specific safety protocols for U-500 insulin. These may include:

• Using only one type of syringe consistently (preferably a TB syringe or a dedicated U-500 syringe if available) to avoid confusion.
• The "teach-back" method, where the patient explains the dose and demonstrates how to draw it up to the pharmacist or nurse to confirm understanding.
• Never using a U-500 vial with an insulin pump unless specifically instructed and programmed by a healthcare professional.
• Always double-checking the dose calculation before every injection.

This calculator is designed to assist in that double-check process, but it is not a substitute for professional medical guidance. Always follow the specific instructions provided by your healthcare team.