The menstrual cycle is an important component of overall health. As such, the menstrual cycle is considered a vital sign by some clinicians.[1] There are a variety of ways to measure menstrual cycle health, ranging from simple, at-home tracking methods to bloodwork and ultrasound imaging. A basic assessment of the menstrual cycle starts with measurements of frequency (menstruation or bleeding occurs every 24 to 38 days), regularity (the number of days between menstruation is similar each month), duration (bleeding does not last longer than eight days), and volume (loss of no more than 80 mL of menstrual blood per cycle).[2] The phases of the menstrual cycle are sometimes measured via basal body temperature and hormone levels in saliva, urine, or blood.[3] If there are abnormalities, like infrequent menstruation (oligomenorrhea), too frequent menstruation (polymenorrhea), the total absence of menstruation (amenorrhea), or very heavy bleeding (menorrhagia), a clinician can perform additional assessments to better understand the underlying cause of the abnormality.
These additional assessments may include bloodwork and imaging. Blood tests can detect the levels of different hormones that affect the menstrual cycle (e.g., progesterone, estrogen, thyroid hormone, androgens, prolactin). They can also measure iron levels, which are sometimes affected by menstrual bleeding, and may aid in the diagnosis of underlying bleeding disorders or infections. In some cases, imaging of the reproductive system is also necessary, usually beginning with an ultrasound. Serial transvaginal ultrasounds can visualize the changes that occur in the ovaries and endometrial lining throughout the menstrual cycle.[4]