Isotretinoin cumulative dose: what it means and how to track it

If you take isotretinoin (Accutane, Clarus, Epuris), you may hear your clinician talk about your "cumulative dose". It sounds technical, but the idea is simple. It is the total amount of isotretinoin you have taken over the whole course.

Why the total matters

For many people, acne clears while they are on isotretinoin. The risk is that it comes back after the course ends. Studies have linked the total amount of drug taken to the chance of a relapse. A higher total, within a safe range, is linked to a lower chance that acne returns.

This is why your clinician does not look only at how your skin looks today. They also look at how much you have taken so far, and how much more is planned.

How cumulative dose is expressed

Cumulative dose is usually written in milligrams per kilogram of body weight (mg/kg). This lets people of different sizes be compared fairly.

Here is the formula:

• Daily dose in mg, multiplied by the number of days you took it, gives the total in mg.
• The total in mg, divided by your body weight in kg, gives the cumulative dose in mg/kg.

Here is an example with made-up numbers. A person weighs 70 kg and takes 40 mg each day for 150 days. The total is 6,000 mg. Divided by 70 kg, that is about 86 mg/kg.

This example is only for learning. It is not a dose or a goal for you.

Target ranges

Clinicians often aim for a total within a target range. Your clinician may choose a different goal for you. Skin that has cleared early may still need the course to continue. Side effects may also mean the course has to stop sooner.

A target is a guide, not a promise. Some people stay clear with a lower total. Others have acne return even after reaching the target.

How to track your dose

Good tracking is simple. Keep these things in one place:

• Your start date. The first day you took a capsule.
• Your daily dose. Write down every change, and the date of the change.
• Missed days. Note days you skipped or took a different amount.
• Your weight. Weigh yourself at the start, and again when your clinician asks.

You can also use our calculator at /tools/isotretinoin-dose-calculator. Enter your weight, your dose and your dates. The tool shows your total so far.

Things that change the number

• A dose change. If your dose goes up or down, calculate each period on its own and add them.
• Weight change. A large change in weight changes the mg/kg figure.
• Taking capsules with food. Isotretinoin is usually taken with a meal that contains fat, because it is absorbed better. If you often take it on an empty stomach, tell your clinician.
• Missed capsules. A short break lowers your total. Do not take extra capsules later to catch up.

What the calculator cannot do

A calculator gives you a number. It does not know your skin, your health, your lab results or your side effects. It does not replace the plan from your clinician.

Do not change your dose to reach a number. Do not stop early, and do not take more than prescribed. Your dose is a clinical decision.

Pregnancy and safety reminder

Isotretinoin can cause serious birth defects. If you can become pregnant, follow the manufacturer's pregnancy prevention program, and follow the rules your clinician gave you.

When to message your clinician

Message your Care Team if:

• you are not sure how many capsules you have taken in total;
• you missed more than a few days, or changed your dose without advice;
• your weight has changed a lot since you started;
• your acne is clear and you wonder whether to stop;
• your acne is not better after several months;
• you have new or serious side effects, such as severe headache, vision changes, low mood or yellow skin;
• you think you may be pregnant. Stop the capsules and contact your clinician right away.

Bring your records to each follow-up. They help your clinician decide how long to continue.