Women thirty-five and older are often acutely aware that their “egg supply” is on the decline. While a literal “egg count” is impossible, the most accurate test for what is medically called ovarian reserve involves measuring the blood level of follicle stimulating hormone (FSH). FSH is produced by the pituitary gland and helps direct the ovaries to mature and release eggs. A rising FSH level indicates a decreasing egg supply, as the pituitary gland pumps out more of the hormone to stimulate ovaries that are no longer responding as they once did. Because the timing of the test is important, women will get the most accurate results by consulting their doctor rather than relying on an over-the-counter test.