Like any other health supplement, even biotin supplements may cause side effects to a few. Normally, when vitamins are used in right quantities, it may not harm health. And biotin belongs to B vitamin group which are not harmful for health. But in case, if there is an overdose then there might be a few problems. However, it is important to note very rarely any such instances are found in which people might have faced any side effects due to biotin supplements. Vitamin B7 is other term used for biotin. One of the study carried out on rats indicated that when high doses of biotin supplements were given to pregnant rats, the possibility of miscarriage increased. However, there are no such evidences that state that this can happen in humans. But it is wise to keep away from any kind of supplement overdose including biotin overdose. But in case even if normal dosages cause some side effects then you must immediately consult your physician. On diagnosis the doctor may come to know that whether it is biotin side effect or some other factor/factors due to which such situation has taken place. In case, if you don’t want to rely on biotin supplements then you must add meat and legumes to your diet.