1. Oral contraceptives – These meds can cause hair loss to many women who use the various birth control devices that contain hormones -- such as the pill, Depo-Provera, or the vaginal “O” ring. Due to changing levels of circulating hormones, the degree of hair loss will vary over time.
2. Anticoagulants or blood thinners – The administration of these drugs can cause a telogen effluvium response with the whole scalp involved. Hair loss typically starts about 12 weeks after first starting on blood thinners.
3. Beta blockers – This medication reduces the workload on the heart, slowing it down a bit. In this way, blood pressure is also lowered. Unfortunately, these drugs can cause a telogenic effect.
4. Male and female hormones – High levels of testosterone or use of anabolic steroids may exacerbate male pattern baldness in men and a general thinning of hair in women. Estrogen and progesterone can also be disruptive to hair growth.
5. Antidepressants – High levels of stress can cause temporary bald spots on the scalp. Depression and anxiety themselves can cause hair loss and so can the medications used to remedy these illnesses due to a telogenic effect.
Because this is a subjective list, and there is a plethora of medications that have an effect on hair growth, here is a fast listing of a fair amount of drugs that could thin your hair out.