Isotretinoin blood tests: what is checked and when?
If you are considering oral isotretinoin for acne, you may have been told that you will need blood tests. That can raise practical questions: what is being checked, how often will tests happen, and could one abnormal result stop treatment?
The short answer is that blood tests are mainly used to monitor your liver and blood fats. Isotretinoin can affect these in some people, often without causing symptoms. Testing gives your prescriber a baseline and helps them decide whether treatment can start or continue safely. The NHS also advises that regular check-ups and blood tests are needed during treatment.[1,5] The exact schedule is individual, so follow the plan given by your own clinical team.
Why are blood tests needed with isotretinoin?
Isotretinoin is a prescription-only medicine considered for severe acne, acne at risk of permanent scarring, or acne that has not responded adequately to appropriate standard treatment. It is not the right treatment for every patient.[2,3]
The medicine can sometimes raise liver enzymes or levels of fats called triglycerides and cholesterol. A blood result is only one part of the safety assessment: your prescriber will also review your acne, medical history, other medicines, side effects, mental health, sexual function and, where relevant, pregnancy-prevention requirements.[2–4]
Blood monitoring is therefore not a pass-or-fail examination. It is information that helps your clinician weigh benefits and risks and adapt the plan to you.
Which blood tests are usually checked?
Liver function tests
These measure substances including liver enzymes. A mild rise does not automatically mean liver damage or that treatment must end. Your clinician will interpret the result in context, compare it with previous results and decide whether to repeat the test, adjust the dose or take another action.
The UK Summary of Product Characteristics (SmPC) for isotretinoin says liver enzymes should be checked before treatment, one month after starting and then at three-monthly intervals, unless more frequent monitoring is clinically indicated.[1]
Blood lipids
A lipid profile checks fats in the blood, particularly triglycerides and cholesterol. The SmPC advises fasting lipid measurements before treatment, after one month and then at three-monthly intervals unless more frequent checks are needed.[1]
Not every laboratory or service handles fasting in exactly the same way. Ask whether you should avoid food beforehand and for how long; do not fast unless you have been instructed to do so.
Other tests when clinically indicated
Some patients need additional or more frequent testing. The SmPC highlights people with diabetes, obesity, higher alcohol intake or a lipid-metabolism disorder, who may need closer checks of lipids and/or blood glucose.[1] Your medicines and wider health history may change what is appropriate.
A full blood count is not listed in the SmPC’s routine liver-and-lipid schedule, although a clinician may request it or other tests for an individual reason. If you are unsure why a test has been ordered, ask what it is intended to monitor.
When will the tests happen?
Testing usually begins before the first dose and is repeated after treatment starts. Your prescriber may change the schedule because of baseline results, dose changes, symptoms, interacting medicines or risk factors such as diabetes or a lipid disorder. Do not copy another person’s timetable or arrange a generic panel without checking which markers and dates your prescriber needs.
Is a pregnancy test the same as an isotretinoin blood test?
No. Pregnancy testing is part of the Pregnancy Prevention Programme for patients of child-bearing potential, but it may use urine rather than blood. Current BAD guidance allows properly supervised home pregnancy testing in suitable circumstances, provided the test meets the required sensitivity and the result is verified by the prescriber.[4]
The Pregnancy Prevention Programme and blood monitoring serve different purposes. Patients who can become pregnant must follow their prescriber’s pregnancy-testing and prevention plan, even if liver and lipid results are normal.[4]
What happens if a result is abnormal?
An out-of-range result does not always mean that isotretinoin is impossible. The next step depends on how abnormal the value is, whether it is changing, your symptoms and your overall risk.
Your clinician may:
repeat the test to confirm the result;
ask about alcohol, diet, medicines, supplements or recent illness;
continue treatment with closer monitoring;
reduce the dose;
pause or stop treatment; or
ask your GP or another specialist to investigate an unrelated cause.
Persistent, clinically relevant rises in liver enzymes may require dose reduction or stopping treatment. Isotretinoin can also raise triglycerides; uncontrolled severe hypertriglyceridaemia can increase the risk of pancreatitis, so it needs clinical action rather than self-management.[1]
Do not change your dose or stop treatment solely because you have seen a flagged laboratory value. Contact the prescribing team promptly so the result can be interpreted safely. Seek urgent medical advice for severe upper abdominal pain, repeated vomiting, yellowing of the skin or eyes, or a severe persistent headache with visual disturbance.
How to prepare for your blood test
Confirm whether you need to fast and what you may drink.
Bring an up-to-date medicine list, including supplements and over-the-counter products.
Report health changes, including recent illness, pregnancy possibility or new symptoms.
Attend at the requested time and ask how results will be reviewed.
Blood tests are only one part of safe monitoring
Current MHRA measures require an appropriately experienced Lead Prescriber to initiate isotretinoin. The first assessment must be in person, although suitable follow-ups may be remote. Patients should be counselled about possible mental-health and sexual-function side effects, assessed before treatment and monitored at follow-up appointments. Patients of child-bearing potential remain within the Pregnancy Prevention Programme.[3,4]
The January 2026 update removed the former requirement for a second prescriber to approve treatment for under-18s, but it did not remove the wider safeguards. All patients should receive current information and complete the updated Acknowledgement of Risk form.[3]
Frequently asked questions
Can I start isotretinoin before my baseline blood results are back?
Your prescriber needs the requested safety information before deciding whether treatment can start. Do not take borrowed or internet-supplied isotretinoin while waiting.
Will I need monthly blood tests?
Not necessarily. Pregnancy testing, clinical reviews and liver/lipid blood tests have different schedules. The SmPC gives a liver-and-lipid schedule of baseline, one month and then three-monthly unless more frequent monitoring is clinically indicated, but your own plan may differ.[1]
Taking the next step
If you have severe, scarring or treatment-resistant acne, a structured assessment can clarify the diagnosis, review treatments already tried and discuss suitable next steps. You can read about mySkinDoc’s doctor-led isotretinoin pathway, including assessment, counselling, blood-test monitoring and follow-up. An appointment is an assessment, not a guarantee of an isotretinoin prescription.
References
Sources checked 19 October 2026.
