Biotin is a B vitamin needed to activate a major enzyme involved in glucose metabolism. In a clinical trial, 43 participants with type 2 diabetes were found to have lower serum biotin levels compared to healthy people without diabetes. Supplementation with 3 mg of biotin three times per day (along with a probiotic) for two months led to normalization of glucose levels. In addition, five participants who continued to take biotin for four years maintained these benefits.¹ In another trial, taking 64.1 micromoles (15 mg) of biotin per day for 28 days led to reductions in high triglyceride levels, but had no effect on glucose or insulin levels in people with type 2 diabetes.² Case reports suggest long-term treatment with high-dose biotin may reduce symptoms of diabetes-related nerve pain.³

It is thought that biotin may have a synergistic effect with chromium. Placebo-controlled trials investigating the effects of taking 600 micrograms of chromium (as chromium picolinate) plus 2 mg of biotin per day have found this combination improves blood glucose control and triglyceride and other lipid levels; however, it is worth noting these trials were funded by the manufacturer of the chromium/biotin supplement they used.^4,5,6,7

Biotin deficiency may occur in as many as 50% of pregnant women.¹² As biotin deficiency in pregnant animals results in birth defects, it seems reasonable to use a prenatal multiple vitamin and mineral formula that contains biotin.

Preliminary studies have found that injecting either the infant or the nursing mother with biotin may be an effective treatment for cradle cap.^13,14 Studies of oral biotin have yielded mixed results in infants. Older preliminary studies and case reports suggest that 4 mg per day of oral biotin might be sufficient for mild cases of cradle cap, but 10 mg per day was required for more severe cases.¹⁵ Two more recent, controlled trials found that oral biotin (4 or 5 mg per day) produced no benefit.^16,17 Thus, the scientific support for using oral biotin to treat cradle cap is weak. The role of biotin in adult seborrheic dermatitis has not been studied.

Biotin deficiency may occur in as many as 50% of pregnant women.¹⁸ As biotin deficiency in pregnant animals results in birth defects, it seems reasonable to use a prenatal multiple vitamin and mineral formula that contains biotin.

Preliminary studies have found that injecting either the infant or the nursing mother with biotin may be an effective treatment for cradle cap.^19,20 Studies of oral biotin have yielded mixed results in infants. Older preliminary studies and case reports suggest that 4 mg per day of oral biotin might be sufficient for mild cases of cradle cap, but 10 mg per day was required for more severe cases.²¹ Two more recent, controlled trials found that oral biotin (4 or 5 mg per day) produced no benefit.^22,23 Thus, the scientific support for using oral biotin to treat cradle cap is weak. The role of biotin in adult seborrheic dermatitis has not been studied.

Biotin, a B vitamin, is known to strengthen hooves in animals. As a result, Swiss researchers investigated the use of biotin in strengthening brittle fingernails in humans, despite the fact that it remains unclear exactly how biotin affects nail structure. An uncontrolled trial of 2.5 mg biotin per day found improved firmness and hardness in almost all cases after an average treatment time of 5.5 months.²⁴ In a controlled trial using 2.5 mg of biotin per day, women with brittle nails, who had their nail thickness measured before and at six to fifteen months after, found their nail thickness increased by 25%. As a result, splitting of nails was reduced. In an uncontrolled study of people who had been taking biotin for brittle nails in America, 63% showed improvement from taking biotin.²⁵ Although the amount of research on the subject is quite limited and positive effects do not appear in all people, those people having brittle nails may want to consider a trial period of at least several months, using 2.5 mg per day of biotin.