The length of time for the effects of biotin intake to manifest vary and are dependent on factors such as the physiology of an individual, dosage and purpose, according to WebMD. Biotin is an enzyme and a type of B vitamin necessary for healthy skin and metabolism.
Researchers from Columbia University have conducted a study on the effect of biotin on brittle nails, notes DurableHealth.com. It documents that 63 percent of participants had improvement in nail strength after six months while on a daily dose of 2,500 micrograms. A study published in the Journal of Clinical and Aesthetic Dermatology on the effect of biotin on thin hair shows a significant increase in hair after 90 to 180 days of treatment.