It does not kill or thin hair that is already present. Because spironolactone is a mild diuretic, its most common side effect is frequent urination for the first 2-3 weeks. Women may also experience a rise in the potassium level. Other side effects are mild uterine cramping, diarrhea, and drowsiness. In addition, patients with regular cycles may experience some irregularity, while some experiencing irregular periods may see them become regular.
Allergic reaction can also occur.
In general, however, side effects are few and mild. In the context of hirsutism, they are best for patients with an enzymatic deficiency. The dosages are usually low. They may cause light-headedness and are therefore best given in the evening. Side effects, usually mild, improve after a couple of weeks of taking the medication.