Biotin supplements are likely effective for treating thinning hair when it is a symptom of biotin deficiency, states the National Institutes of Health's MedlinePlus. There is no adequate evidence as of 2015 to substantiate the claim that biotin is useful for hair loss when it is taken by mouth together with zinc.
Biotin is an essential component of enzymes in the body that helps in breaking down fats and carbohydrates, according to MedlinePlus. It is also known as a B complex vitamin or vitamin H. Hair thinning occurs when an individual experiences a biotin deficiency. There is no efficient laboratory test to detect the deficiency. A doctor notices it by observing the symptoms.
Taking vitamins help to improve keratin in the body, but it is not clear what role biotin plays, notes the Huffington Post. Hair loss can occur due to other causes and biotin supplements can possibly help to correct and even reverse the condition. The daily recommended dose for biotin supplements is 2.5 milligrams. A doctor needs to be consulted about the proper dose for a full effect. Taking an overdose can lead to other side effects, such as lower vitamin C levels, skin rashes, a slower discharge of insulin and elevated blood sugar levels.