💊 Isotretinoin Dose Calculator

Isotretinoin dosing is built around a cumulative target: 120 to 150 mg per kilogram of body weight over the whole course. Hitting that total predicts long-term remission far better than any particular daily dose. Daily dosing usually runs 0.5 to 1 mg/kg/day, and the course length falls out of the arithmetic: total divided by daily dose.

This calculator shows the daily milligrams, the cumulative target, and the estimated months to get there. It is a planning aid for understanding your prescription, not a way to set one: isotretinoin is tightly regulated, teratogenic, and monitored with monthly labs.

How to Use This Calculator

Enter weight in kilograms and pick the daily dose intensity your dermatologist discussed (0.5 low, 1.0 standard). Choose the cumulative target within 120 to 150 mg/kg. Read the daily milligrams, the total course milligrams, and the estimated duration. Expect the real prescription to round to available capsule strengths.

Why Cumulative Dose Rules

The cumulative-dose concept comes from long-term follow-up studies: patients reaching 120 to 150 mg/kg relapsed far less than those stopped early, regardless of daily intensity. Lower daily doses with longer courses reach the same total with fewer side effects, which is why many dermatologists now favor 0.5 mg/kg/day stretched over more months. Capsules come in fixed strengths (commonly 10, 20, 30, 40 mg), so prescribers approximate the computed daily milligrams with combinations, sometimes alternating doses across days.

Worked Example

A 70 kg patient at 0.75 mg/kg/day takes 53 mg/day, aiming for 9,450 mg (135 mg/kg) total. At that pace the course runs 5.9 months. Note 53 mg is not a standard capsule size: prescribers round to available strengths: real prescriptions use 10, 20, 30, or 40 mg capsules, so the dermatologist rounds to the nearest workable combination, often 40 mg plus 20 mg on alternate days or similar.

Reading Your Course Plan

The daily milligrams tell you what each day looks like; the cumulative total tells you when you are done. If side effects force a dose reduction, the course simply lengthens to protect the cumulative target. Stopping early at, say, 80 mg/kg leaves relapse risk on the table, which is the main reason dermatologists emphasize finishing. Monthly monitoring (lipids, liver tests, pregnancy tests under the US iPLEDGE program) is part of every course, not optional.

Isotretinoin Demands Medical Supervision

Isotretinoin causes severe birth defects: anyone who could become pregnant must use two forms of contraception and follow iPLEDGE requirements in the US. It can raise triglycerides and liver enzymes, cause severe dryness, and is linked with mood changes that deserve prompt attention. Never share capsules or start a course without a dermatologist. This tool is for informational purposes only, not medical advice. Dosing decisions must be confirmed with your doctor or pharmacist. Consult a healthcare professional.

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For informational purposes only, not medical advice. Dosing decisions must be confirmed with your doctor or pharmacist. Consult a healthcare professional.