No single test can diagnose premenstrual syndrome (PMS). A diagnosis of PMS or the more severe form, premenstrual dysphoric disorder (PMDD), is usually based on a medical history and a two- or three-cycle menstrual diary that records daily symptoms, menstruation days, and ovulation days, if possible. Because it's important for your health professional to rule out other conditions that cause PMS-like symptoms, it may take more than one visit to diagnose your symptoms. See an example of a menstrual diary(What is a PDF document?).

Because treatable thyroid problems sometimes cause PMS-like symptoms, you may have a thyroid-stimulating hormone (TSH) blood test to make sure that your thyroid gland is working properly.

Diagnosing PMS may be difficult when a woman has another condition that is made worse during the last 2 weeks of her menstrual cycle.

• Although there are clearcut criteria for diagnosing premenstrual syndrome, PMS-like symptoms often blend in with those of other conditions.
• All symptoms need to be evaluated and treated.

Knowing whether your symptoms are premenstrual helps you and your health professional decide on the best treatment for you. By definition, PMS and PMDD occur only during the phase between ovulation and the start of menstrual bleeding. Traditionally, ovulation was thought to happen 14 days before the next menstrual period, or on day 15 of a 28-day cycle. However, recent research suggests that ovulation dates vary widely from woman to woman and from month to month.⁸ Women with irregular cycles have a wide range of possible ovulation days.

You can most accurately pinpoint your ovulation day by monitoring your cervical mucus, your basal body temperature, and your luteinizing hormone (LH) changes.⁷