Why Is My Period Late? 10 Common Causes (Besides Pregnancy)

1. Early Pregnancy: The most common physiological cause of missed menses in sexually active individuals of reproductive age. 2. Emotional or Physical Stress: High cortisol and CRH levels suppress hypothalamic GnRH secretion, delaying LH surges and ovulation. 3. Polycystic Ovary Syndrome (PCOS): Elevated anovulatory androgen levels lead to irregular, delayed, or missed cycles. 4. Thyroid Dysfunction: Both Hypothyroidism (underactive) and Hyperthyroidism (overactive) alter TSH and prolactin, impairing cycle regularity. 5. Stopping Hormonal Contraception: HPO axis reactivation after birth control pills or Depo-Provera injection can take 1 to 6+ months. 6. Low Energy Availability & RED-S: Restrictive dieting, sudden weight loss, or intense athletic training can trigger Functional Hypothalamic Amenorrhea (FHA). 7. Perimenopause Transition: Individuals in their 40s may experience variable cycle lengths as ovarian follicular pools decline. 8. Recent Illness or Infection: Systemic physiological stress temporarily delays follicular maturation. 9. Certain Medications: Antipsychotics, antidepressants, thyroid meds, or chemotherapy can affect prolactin and cycle timing. 10. Normal Cycle Variation: Menstrual cycles naturally vary by a few days from month to month without underlying pathology. 11. Postpartum & Lactation: For individuals who have recently given birth, understanding when periods return after having a baby depends on breastfeeding frequency, lochia recovery, and prolactin levels.

If you are sexually active, take a home urine pregnancy test 1 day after your expected menses or 14 days following potential exposure. Modern hCG blood and urine tests provide definitive early confirmation.

Consult a primary care clinician or gynecologist if you miss 3 consecutive periods (secondary amenorrhea), experience severe pelvic pain, or notice sudden hirsutism (excess facial/body hair) or severe acne.