Blood tests while taking isotretinoin: what is checked and why
Isotretinoin is one of the most effective treatments for severe acne, but it requires careful monitoring. Our editorial team explains which blood tests are carried out, why, and how training can affect the results.
Why isotretinoin needs monitoring
Isotretinoin is an oral retinoid, chemically related to vitamin A, used for severe acne that has not responded to other treatments. It shrinks the sebaceous glands, reduces oil production and has a high rate of long-term remission. It is highly effective, but it also affects metabolism, the liver and the developing foetus, so treatment comes with a structured monitoring programme.
In the UK, isotretinoin can only be prescribed by or under the supervision of a consultant dermatologist. Following a review by the Commission on Human Medicines, the MHRA introduced strengthened safety measures in 2023, including closer assessment of mental health and sexual function and, for patients under 18, agreement from two independent prescribers before starting.
Blood tests are one part of this programme. They are designed to detect problems early – most commonly changes in blood fats and liver enzymes – and, for people who could become pregnant, to confirm that there is no pregnancy before and during treatment.
Many people who take isotretinoin are young and physically active, so this article also explains how training can influence some results.
Which tests and when
The exact schedule depends on the dermatology team and local protocols, but UK practice follows national guidance and product information. A typical framework looks like this.
| Test | Before treatment | During treatment | After treatment |
|---|---|---|---|
| Pregnancy test (if able to become pregnant) | Yes, supervised | Regularly, usually every month | About one month after stopping |
| Liver function tests (ALT, AST) | Yes | Usually after about one month, then as indicated | Not usually needed |
| Fasting lipids (triglycerides, cholesterol) | Yes | Usually after about one month, then as indicated | Not usually needed |
| Full blood count, glucose | Sometimes | If clinically indicated | Rarely |
| Creatine kinase | Not routine | If muscle symptoms occur | Not routine |
Mental health assessment is also part of monitoring, though not a blood test. Patients are asked about mood, anxiety and thoughts of self-harm before and during treatment, and family members are encouraged to report any changes they notice.
What the evidence says about routine blood tests
A systematic review and meta-analysis by Lee and colleagues in 2016 found that clinically significant abnormalities in liver function and blood count were uncommon during isotretinoin treatment, and that triglyceride and cholesterol increases were more frequent but rarely severe. The authors suggested that frequent repeat testing in healthy patients might not be necessary.
US guidelines from the American Academy of Dermatology, updated by Reynolds and colleagues in 2024, similarly support a more streamlined approach to laboratory monitoring in healthy patients. UK practice remains broadly cautious and may vary between centres, so follow your dermatologist's plan rather than general advice.
Severe hypertriglyceridaemia is uncommon but important because very high triglycerides can cause pancreatitis. People with a personal or family history of lipid disorders, diabetes, obesity or heavy alcohol use may need closer monitoring.
Exercise and test results
Strenuous exercise can affect several blood markers, and this is particularly relevant for people who train while taking isotretinoin.
- Creatine kinase (CK): heavy resistance training or long runs can raise CK significantly for several days, which can be mistaken for drug-related muscle damage.
- Liver enzymes: AST and, to a lesser extent, ALT are also found in muscle and may rise after intense training.
- Triglycerides: a large meal or alcohol the evening before can increase levels; fasting tests are more reliable.
A practical approach is to avoid unusually intense or unfamiliar training for 48–72 hours before scheduled blood tests, to avoid alcohol the day before and to tell the person taking the sample about recent exercise. This helps the dermatology team interpret results correctly.
Isotretinoin itself can cause muscle and joint aches. Persistent muscle pain, weakness or dark urine should be reported promptly, because they may indicate significant muscle breakdown requiring CK testing.
Other practical considerations
Isotretinoin must not be combined with vitamin A supplements, because of the risk of vitamin A toxicity, or with tetracycline antibiotics, because of the risk of raised intracranial pressure. Check multivitamins and sports supplements for vitamin A content.
Patients should not donate blood during treatment and for at least one month afterwards, because of the risk to a pregnant recipient. Alcohol should be limited, as it can raise triglycerides and strain the liver.
Isotretinoin is not on the WADA Prohibited List, so competing athletes can use it when prescribed, but they should tell their team doctor because of its effects on skin, muscles and recovery.
Editorial team's conclusions
Blood tests during isotretinoin treatment focus mainly on pregnancy testing, liver function and blood lipids, alongside regular mental health assessment.
Significant laboratory abnormalities are uncommon in healthy patients, and guidance is moving towards more targeted monitoring, but you should follow your dermatology team's plan.
Intense exercise can affect CK and liver enzymes, so plan training around blood tests and tell the clinic about recent workouts.
Related topics on our site include liver function tests for people who train, creatine kinase and exercise, and acne in athletes.
References
- Lee YH, Scharnitz TP, Muscat J, et al. Laboratory monitoring during isotretinoin therapy for acne: a systematic review and meta-analysis. JAMA Dermatol. 2016;152(1):35–44.
- Zaenglein AL, Pathy AL, Schlosser BJ, et al. Guidelines of care for the management of acne vulgaris. J Am Acad Dermatol. 2016;74(5):945–973.
- Reynolds RV, Yeung H, Cheng CE, et al. Guidelines of care for the management of acne vulgaris. J Am Acad Dermatol. 2024;90(5):1006.e1–1006.e30.
- National Institute for Health and Care Excellence. Acne vulgaris: management. NICE guideline NG198. London: NICE; 2021.
- Layton A. The use of isotretinoin in acne. Dermatoendocrinol. 2009;1(3):162–169.
- Medicines and Healthcare products Regulatory Agency. Isotretinoin: introduction of new safety measures, including additional oversight of the initiation of treatment for patients under 18 years of age. Drug Safety Update. London: MHRA; 2023.
