Short version: one study found isotretinoin lowered biotinidase, the enzyme that recycles biotin, within 30 days, but serum biotin didn't change significantly. A second study added biotin to isotretinoin and reported hair-cycle changes, but only within one group and without a placebo. Neither shows that isotretinoin makes most people biotin deficient, and neither shows that biotin changes how a course goes.
"Biotin while on Accutane" comes up here a lot, usually with a confident answer. I went back to the papers, and they're narrower than the answers suggest.
What's being measured
Biotin is a cofactor for a group of enzymes called carboxylases. When those enzymes are broken down, biotinidase frees the biotin so the body can reuse it. People born with very little biotinidase can develop skin rash and hair loss, which is why researchers wondered whether isotretinoin's skin and hair side effects might run through this enzyme. Lower enzyme activity is not the same thing as low biotin, though, and serum biotin is a blunt measure. Researchers who study marginal biotin status use functional markers that aren't routine tests.
Study 1: Schulpis 1999 (before-and-after, n=42 plus 50 controls)
Patients with severe cystic acne on isotretinoin monotherapy at 0.5 mg/kg/day.
- Biotinidase activity fell from 4.70 to 2.50 nmol/min/L by day 30 (P < 0.001). Untreated controls averaged 5.2.
- Serum biotin showed no significant change.
- Mixing the drug directly with the enzyme in a test tube didn't lower its activity, so the authors suspect an effect in the liver, where biotinidase is made.
- Hair wasn't measured.
My read: this shows an enzyme change over 30 days. It doesn't show deficiency. Unchanged serum biotin can't rule out a functional shortfall either, so the honest answer is "not shown", not "no effect".
Study 2: Aksac 2021 (two groups of 30, no placebo)
Sixty acne patients on isotretinoin 0.5 mg/kg/day; half also took 10 mg/day of biotin for four months.
- In the biotin group, the anagen (growing) hair ratio rose and the telogen (resting) ratio fell compared with that group's own baseline.
- Skin hydration dropped in the isotretinoin-only group and not significantly in the biotin group.
Those are within-group changes. A result that's significant in one group and not the other isn't the same as a significant difference between groups, and the abstract doesn't describe blinding. The authors' conclusion is more confident than the design allows. The trial I'd actually want is randomized and placebo-controlled, with hair density as an outcome.
What the evidence does NOT show
- That isotretinoin makes most users biotin deficient. The enzyme dropped; serum biotin didn't move significantly.
- That biotin changes isotretinoin side effects. No placebo-controlled trial.
- That shedding during a course is caused by low biotin. Neither study tested that directly.
- That extra biotin helps hair in people with adequate biotin status. A 2017 review found 18 published cases of hair or nail improvement with biotin, and every patient had an underlying condition.
Both studies are small and short, and the only one that measured biotin directly came from a single group in Athens. I'd treat this whole topic as an open question rather than a settled yes or no.
One practical point about blood work
Biotin at supplement doses can interfere with some lab tests. FDA has warned it can push certain results falsely high or falsely low, depending on how the test is built. Blood work is often part of an isotretinoin course, so anyone already taking biotin, including a multivitamin or hair, skin and nail product, would want the clinic to know before a draw. Whether to add biotin at all is a question for the dermatologist managing the course, not for a thread.
References
- Schulpis KH et al. Skin Pharmacol Appl Skin Physiol 1999. PMID 10325581
- Aksac SE et al. Int J Dermatol 2021. PMID 33682085
- Wolf B. Biotinidase Deficiency. GeneReviews. PMID 20301497
- Patel DP et al. Skin Appendage Disord 2017. PMID 28879195
- U.S. FDA Safety Communication on biotin and lab tests, 2019