The clomiphene challenge test is used to check the egg supply (ovarian reserve), usually in women in their 30s and 40s who are considering using reproductive technology to conceive. It can also be used for younger women when ovulation medicine has not worked.

The clomiphene challenge test is done over many days. Clomiphene is a fertility medicine that stimulates the pituitary to release hormones that cause the ovaries to release eggs. A blood test to measure a woman's follicle-stimulating hormone (FSH) level is done on days 3 to 5 of her menstrual cycle, followed by 5 days of an oral dose of clomiphene. On day 10, blood FSH levels are measured again. If a woman's ovarian reserve is normal, FSH levels tend to return to normal by day 10. But an elevated FSH level on days 3 to 5 or day 10 may mean a low ovarian reserve. A high FSH level can be a sign that the ovaries are having trouble releasing eggs.