Isotretinoin Dose Calculator – Daily Dose & Duration Planner

Isotretinoin, most commonly known by the brand name Accutane, is an oral retinoid (vitamin A derivative) used as the definitive treatment for severe nodular acne and cases that have not responded to antibiotics and topical therapy. Unlike most acne treatments that must be taken indefinitely to maintain effect, isotretinoin can produce prolonged remission — and in many patients complete cure — after a single course. The key to achieving lasting results lies in reaching a sufficient cumulative dose. The cumulative dose concept is central to isotretinoin therapy. Clinical evidence, most extensively from the work of Cunliffe and colleagues published in the 1980s and 1990s, established that relapse rates fall dramatically when the total dose across an entire course reaches approximately 120–150 mg per kilogram of body weight. Below this threshold — for example at 80–100 mg/kg — relapse rates are significantly higher, even if the skin has cleared during treatment. This is why dermatologists calculate the target total milligrams not in absolute terms but per kilogram: a 50 kg patient aiming for 120 mg/kg needs 6,000 mg total, while an 80 kg patient needs 9,600 mg. The daily dose is typically started between 0.5 mg/kg/day and 1.0 mg/kg/day. Lower starting doses (0.5 mg/kg/day) are associated with fewer side effects, particularly the initial acne flare that can occur in the first few weeks. Higher doses (1.0 mg/kg/day) may clear acne faster but carry more adverse effects including dry skin, cheilitis (cracked lips), elevated liver enzymes, and hyperlipidemia. Some dermatologists prefer a low-dose extended protocol (0.25–0.4 mg/kg/day for longer periods) as an alternative strategy, particularly for mild-to-moderate acne. When a specific daily dose in milligrams is prescribed — for example, 40 mg/day for a 70 kg patient — it effectively implies a per-kilogram dose of approximately 0.57 mg/kg/day for that patient. Fixed-milligram dosing is often used in practice because commercially available capsule strengths (10 mg, 20 mg, 40 mg) may not allow perfect weight-based dosing. This calculator allows you to enter either method: the per-kilogram rate or a custom fixed daily dose. Side effects monitoring is as important as dose calculation. Isotretinoin has a well-established teratogenicity risk — it causes severe birth defects — so women of childbearing potential must use two forms of contraception and comply with a risk-management program (iPLEDGE in the United States). Regular blood tests for liver enzymes (ALT, AST) and lipids (triglycerides, cholesterol) are standard. Mood changes, including depression, have been reported, though the causal relationship is debated. Always discuss all side effects and monitoring requirements with your dermatologist before starting treatment.