Isotretinoin Cumulative Dose Calculator
Enter body weight and target cumulative dose to get total course dose in mg, duration in months and daily intensity in mg/kg/day. Handles both a single fixed dose and step-up schedules such as 20 mg → 30 mg → 40 mg.
Last updated 2 September 2026 · references checked against AAD 2024 and EuroGuiDerm 2025Already on treatment? Track how much is left
Send the weight, daily dose, cumulative target, course length and expected finish date to your inbox, so you can check progress at each follow-up visit.
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Phase-by-phase breakdown
Each phase contributes its own share of the cumulative total. The teal row is the extra time needed at the final dose to reach the target.
| Phase | Dose | mg/kg/day | Duration | Delivered | Cumulative |
|---|
How long is the course at each cumulative target?
Same patient, same daily dose — only the cumulative target changes. Your selected target is highlighted.
Filled in below for a worked example of a 70 kg patient at 40 mg/day. Enter a weight above and the table recalculates for that patient.
| Cumulative target | Total dose | Days | Months |
|---|---|---|---|
| 100 mg/kg | 7,000 mg | 175 | 5.7 |
| 120 mg/kg | 8,400 mg | 210 | 6.9 |
| 150 mg/kg | 10,500 mg | 263 | 8.6 |
| 220 mg/kg | 15,400 mg | 385 | 12.6 |
Worked examples: isotretinoin cumulative dose by body weight
The arithmetic is simple: total course dose = body weight in kg × cumulative target in mg/kg, and course length in days = total dose ÷ daily dose. The tables below are pre-calculated at a daily dose of 40 mg, so the numbers can be read without entering anything.
70 × 120 = 8,400 mg in total. At 40 mg/day that is 8,400 ÷ 40 = 210 days, about 6.9 months, at a daily intensity of 40 ÷ 70 = 0.57 mg/kg/day — inside the conventional 0.5–1.0 mg/kg/day band. Total dose and course length at 120 mg/kg (40 mg/day)
| Body weight | Total course dose | Days at 40 mg/day | Months |
|---|---|---|---|
| 50 kg (110 lb) | 6,000 mg | 150 | 4.9 |
| 60 kg (132 lb) | 7,200 mg | 180 | 5.9 |
| 70 kg (154 lb) | 8,400 mg | 210 | 6.9 |
| 80 kg (176 lb) | 9,600 mg | 240 | 7.9 |
| 90 kg (198 lb) | 10,800 mg | 270 | 8.9 |
| 100 kg (220 lb) | 12,000 mg | 300 | 9.9 |
Total dose and course length at 150 mg/kg (40 mg/day)
| Body weight | Total course dose | Days at 40 mg/day | Months |
|---|---|---|---|
| 50 kg (110 lb) | 7,500 mg | 188 | 6.2 |
| 60 kg (132 lb) | 9,000 mg | 225 | 7.4 |
| 70 kg (154 lb) | 10,500 mg | 263 | 8.6 |
| 80 kg (176 lb) | 12,000 mg | 300 | 9.9 |
| 90 kg (198 lb) | 13,500 mg | 338 | 11.1 |
| 100 kg (220 lb) | 15,000 mg | 375 | 12.3 |
Worked example of a step-up (titration) schedule
A dose that changes part-way through is where cumulative-dose arithmetic usually goes wrong: each phase contributes only its own days × daily dose, and the final dose then continues until the target is met. For a 70 kg patient with a 120 mg/kg target (8,400 mg) started low to blunt an early flare:
| Phase | Daily dose | mg/kg/day | Duration | Delivered | Cumulative |
|---|---|---|---|---|---|
| 1 | 20 mg | 0.29 | 30 days | 600 mg | 600 mg |
| 2 | 30 mg | 0.43 | 30 days | 900 mg | 1,500 mg |
| 3 | 40 mg | 0.57 | 173 days (to target) | 6,900 mg | 8,400 mg |
Total course length 233 days ≈ 7.7 months — about 23 days longer than the same patient held at 40 mg/day from day one. Use Step-up schedule mode in the calculator above to model any other combination, or to enter what a patient has already taken and see what is left.
Quick conversions
Isotretinoin: 13 questions answered with the current evidence
Isotretinoin is the single most effective treatment for severe and treatment-resistant acne — and the most misunderstood. Much of what circulates online dates from the 1980s, or from case reports that larger studies have since failed to confirm. Each answer below is anchored to a linked source.
🗂️ Quick reference summary
- How long does isotretinoin take to work?
- Is a 10 mg daily dose effective?
- What are the side effects?
- Does isotretinoin cause purging?
- Does it cause permanent side effects?
- Does it cause depression or anxiety?
- Does it cause hair loss?
- Can acne come back afterwards?
- What if I stop before finishing the course?
- What if I get pregnant while taking it?
- Is laser hair removal safe on isotretinoin?
- What skincare products can I use?
- When should isotretinoin be stopped?
How long does isotretinoin (Accutane) take to work?
Oiliness falls within the first 2–4 weeks; visible improvement in lesions usually begins at 4–8 weeks. A standard course runs about 4 to 5 months, and the skin often continues to clear for a period after the medication is stopped.
Roughly 85% of patients respond within a 4-month course, while about 15% need longer — occasionally up to 10 months. Slow responders often have macrocomedones or an underlying hormonal driver.
📚 Reference: American Academy of Dermatology — Isotretinoin FAQs ↗
Is a 10 mg daily dose of isotretinoin effective for acne?
Yes for most moderate acne, but it takes longer. In a prospective study of 150 patients given a fixed 10 mg daily dose until a cumulative dose of 90–110 mg/kg, all achieved total clearance at a mean of 24 weeks, with mild relapse in only 4%. Patients with severe or very severe acne took considerably longer to clear (32.9 vs 19.1 weeks).
| Regimen | Typical time to clearance | Positioning |
|---|---|---|
| 10 mg/day (low dose) | ~24 weeks | Moderate acne |
| 0.5–1.0 mg/kg/day (conventional) | ~16–20 weeks | Severe / nodulocystic |
📚 Reference: Yap FB-B. Fixed-dose 10 mg daily isotretinoin for acne vulgaris. J Cosmet Dermatol 2017 ↗
What are the side effects of isotretinoin (Accutane)?
Almost every isotretinoin side effect is dose-related and reverses after the course ends. The common adverse effects are mucocutaneous, musculoskeletal and ophthalmic — dry lips, dry skin, sun sensitivity, joint and muscle aches, and dry eyes — and they generally resolve after the drug is stopped with standard courses.
| System | Typical effects | Frequency |
|---|---|---|
| Mucocutaneous | Cheilitis, xerosis, skin fragility, photosensitivity | Near-universal |
| Ocular | Dry eyes, contact lens intolerance | Common |
| Musculoskeletal | Myalgia, arthralgia, back pain | Common |
| Laboratory | Raised triglycerides, raised transaminases | Uncommon / usually mild |
| Reproductive | Teratogenicity | Absolute contraindication |
Recommended monitoring includes liver function tests, a fasting lipid panel, and pregnancy testing for anyone who can become pregnant. Routine full blood count monitoring is not needed in otherwise healthy patients.
📚 Reference: AAD Guidelines of Care for the Management of Acne Vulgaris, JAAD 2024 ↗
Ten body systems in tick-box form — skin, eyes, nose, mouth, mood, joints, gut and the laboratory abnormalities to watch. Print it and fill it in before each appointment.
Sends the checklist link to your inbox. Occasional dermatology updates after. Unsubscribe any time.
Does isotretinoin (Accutane) cause purging?
An early flare is real but not universal. Studies report an initial acne flare in up to about 32% of patients during the first month, mostly mild to moderate in severity.
It is more likely in severe, inflammatory, widespread cystic acne, and can be blunted by starting at a lower dose or adding a short course of prednisone in the first month.
📚 Reference: Acute Acne Flare Following Isotretinoin Administration, Dermatology (Karger) ↗
Does isotretinoin (Accutane) cause permanent side effects?
Most effects are dose-related and reverse after stopping. In a propensity-matched analysis of 61,894 pairs followed for 6–10 years, isotretinoin was not associated with increased inflammatory bowel disease (HR 0.88) or ulcerative colitis, and lipid elevations were transient.
The genuinely permanent risks are fetal malformation from pregnancy exposure, and scarring from waxing — which must be avoided during treatment and for six months afterwards.
📚 Reference: Gupta N, et al. Isotretinoin Does Not Increase the Risk of IBD: TriNetX Cohort. J Drugs Dermatol 2025 ↗
Does isotretinoin (Accutane) cause depression or anxiety?
Population-level data are reassuring. A meta-analysis of 25 studies including 1,625,891 participants found the 1-year absolute risk of completed suicide, suicide attempt, suicidal ideation and self-harm each below 0.5%, and depression at 3.83%. There was no increased relative risk of psychiatric disorders overall, and isotretinoin users were less likely than non-users to attempt suicide 2 to 4 years after treatment.
📚 Reference: Tan NKW, et al. Risk of Suicide and Psychiatric Disorders Among Isotretinoin Users. JAMA Dermatol 2024 ↗
Does isotretinoin (Accutane) cause hair loss?
Uncommon and typically reversible. A systematic review of 22 studies found hair loss in 3.2% of patients on <0.5 mg/kg/day versus 5.7% on ≥0.5 mg/kg/day.
The pattern is telogen effluvium — diffuse, non-scarring shedding. Because the follicles are not damaged, regrowth is expected over roughly 3 to 12 months after stopping. Lowering the daily dose is a reasonable option when shedding is distressing.
📚 Reference: Lytvyn Y, et al. Frequency of isotretinoin-induced hair loss by dose. JAAD International 2022 ↗
Can acne come back after isotretinoin (Accutane)?
In a minority of patients, yes. Among 19,907 patients who completed a course, 22.5% relapsed and 8.2% needed a second isotretinoin course. Higher cumulative dosage was associated with lower rates of both, while female sex predicted higher relapse (HR 1.43). Median time to relapse was 7.5 months.
📚 Reference: Lai J, Barbieri JS. Acne Relapse and Isotretinoin Retrial. JAMA Dermatol 2025 ↗
What happens if I stop isotretinoin before completing the course?
There is no withdrawal syndrome and no taper is needed, but relapse becomes more likely. In a study of 212 patients the overall relapse rate was 37.3%, and was significantly higher in those who still had residual lesions at the end of treatment. The authors advise continuing until complete clinical clearance and then for at least one further month, regardless of cumulative dose.
A larger review of 1,453 patients found that neither daily nor cumulative dose influenced relapse — provided treatment continued for at least 2 months after the acne had fully resolved.
📚 Reference: Demirci Saadet E. Relapse rate and factors after oral isotretinoin. Dermatol Ther 2021 ↗
What happens if I get pregnant while taking isotretinoin (Accutane)?
Stop isotretinoin at once and contact the prescriber. The FDA label directs that the drug be discontinued immediately and the patient referred to an obstetrician experienced in reproductive toxicity for further evaluation and counselling. Any suspected fetal exposure during treatment or within one month afterwards must be reported.
Major congenital malformations, spontaneous abortion and premature birth have all been documented, and there is no accurate way to determine whether an exposed fetus has been affected.
📚 Reference: FDA Prescribing Information — Isotretinoin Capsules (DailyMed) ↗
Is laser hair removal safe while on isotretinoin?
Current expert consensus supports it, despite the older six-month rule. A systematic review of 32 publications covering 1,485 procedures found insufficient evidence to justify delaying manual dermabrasion, superficial chemical peels, cutaneous surgery, laser hair removal, or fractional ablative and non-ablative lasers in patients currently on or recently finished with isotretinoin.
A controlled study of alexandrite, diode and Nd:YAG laser hair removal found no significant difference in side effects versus controls — no blistering, ulceration, keloid or scar formation in either group.
| Procedure | Consensus position |
|---|---|
| Laser hair removal (alexandrite, diode, Nd:YAG) | Insufficient evidence to delay |
| Non-ablative & fractional ablative lasers | Insufficient evidence to delay |
| Superficial chemical peels, minor surgery | Insufficient evidence to delay |
| Mechanical dermabrasion | Not recommended |
| Fully ablative resurfacing | Not recommended |
| Waxing (hot or cold) | Avoid — during + 6 months after |
📚 Reference: Spring LK, et al. Isotretinoin and Timing of Procedural Interventions. JAMA Dermatol 2017 ↗
What skincare products can I use while taking isotretinoin (Accutane)?
Three products are enough: a gentle non-foaming cleanser, a non-comedogenic moisturiser and an oil-free SPF 30+ sunscreen — everything acidic or exfoliating comes off the shelf until the course ends. Apply a non-comedogenic moisturiser while the skin is still damp after cleansing, avoid abrasive scrubs and exfoliating cleansers, use petroleum jelly or lip balm for dry lips, and use an oil-free broad-spectrum sunscreen of SPF 30 or higher every morning.
| Category | Guidance |
|---|---|
| Gentle, non-foaming cleanser | Use |
| Non-comedogenic moisturiser (ceramides, squalane) | Use |
| Broad-spectrum SPF 30+ sunscreen, oil-free | Use daily |
| Petrolatum lip balm | Use frequently |
| Topical retinol / retinoids | Avoid |
| Benzoyl peroxide or sulfur | Avoid |
| Vitamin C serums | Avoid |
| AHA / BHA exfoliants (glycolic, salicylic, lactic) | Avoid |
| Vitamin A supplements | Avoid |
| Waxing | Avoid + 6 months after |
📚 Reference: American Academy of Dermatology — Isotretinoin: Side Effects and Skin Care ↗
When should isotretinoin be stopped? What is the current recommended endpoint?
The endpoint is clinical, not arithmetic. Continue isotretinoin until the patient is clear of active inflammatory acne, and then keep going for at least one further month — often one to two months — before stopping. The familiar 120–150 mg/kg cumulative range is used as a planning guide, not as an absolute requirement that must be reached before treatment can end.
| Situation at the planned end date | What the guideline supports |
|---|---|
| Clear, and has stayed clear for 1–2 months | Stop |
| Clear only in the last few weeks | Continue 1–2 more months |
| Residual active inflammatory lesions | Do not stop yet |
| 120–150 mg/kg reached but acne still active | Cumulative target alone is not a reason to stop |
| Clear and stable, but below 120 mg/kg | Stopping is reasonable |
📚 Reference: EuroGuiDerm Guideline for the Treatment of Acne — Update 2025 (JEADV, short version) ↗ · Summary of the isotretinoin dosing recommendations ↗
A one-page summary of the 2025 update — dosing recommendations, the cumulative-dose position, corticosteroid combination and the stopping endpoint, with the source references.
Sends the summary link to your inbox. Occasional guideline updates after. Unsubscribe any time.
🔗 Related isotretinoin references
Questions this calculator does not cover — taking isotretinoin with a fatty meal, soya or peanut allergy, alcohol, male fertility, and pregnancy while the male partner is treated — are answered in the clinician FAQ.
References
- Reynolds RV, Yeung H, Cheng CE, et al. Guidelines of care for the management of acne vulgaris. J Am Acad Dermatol. 2024.
- Cohort analysis of acne relapse and isotretinoin retrial. JAMA Dermatology. 2025;161(4):367–374. doi:10.1001/jamadermatol.2024.5416
- Tan J, Knezevic S, Boyal S, et al. Evaluation of evidence for acne remission with oral isotretinoin cumulative dosing of 120–150 mg/kg. J Cutan Med Surg. 2016;20:13–20.
- Blasiak RC, et al. High-dose isotretinoin treatment and the rate of retrial, relapse and adverse effects. JAMA Dermatol. 2013.
Medical disclaimer: This calculator is an educational reference for clinicians and patients already under dermatological care. It does not constitute medical advice, does not account for comorbidities, drug interactions, hepatic or lipid abnormalities, or pregnancy status, and must not be used to start, stop or alter isotretinoin therapy without a licensed prescriber.