Progesterone: how it works and why it matters

Progesterone is one of the main female sex hormones. If you track cycles, try to get pregnant, or are dealing with irregular periods, this hormone matters a lot. It helps prepare the uterus for pregnancy, supports early pregnancy, and balances estrogen. Low or high levels can change your period, mood, sleep, and even bone or heart health over time.

How progesterone usually behaves

After ovulation your body makes more progesterone in the corpus luteum. If an egg isn’t fertilized, levels fall and your period starts. If pregnancy happens, progesterone stays high to keep the uterine lining healthy. No ovulation means low luteal progesterone — that’s common with PCOS or stress-related menstrual changes. Tests usually check blood levels in the luteal phase (about a week before your period). Saliva tests exist but blood serum is the standard for doctors.

There’s natural progesterone and synthetic progestins. They do similar jobs but act differently in the body. Medroxyprogesterone (Provera) is a common progestin used to regulate periods and for certain medical needs. Bioidentical progesterone creams or pills are marketed widely, but evidence and dosing can vary — talk to your clinician before switching treatments.

When to think about testing or treatment

Consider a test if you have missed periods, heavy or very light bleeding, trouble conceiving, repeated miscarriages, or symptoms that follow ovulation like mood swings or breast tenderness. If you have PCOS or anovulatory cycles, addressing insulin resistance and lifestyle can improve ovulation and progesterone production. For fertility workups, doctors often measure mid-luteal progesterone to confirm ovulation.

Treatments include short courses of progestins to trigger a period, progesterone supplements during luteal phase for IVF or some fertility plans, and hormone replacement therapy that pairs estrogen with progesterone to protect the uterine lining. Each choice depends on your goal: cycle control, contraception, fertility support, or menopausal symptom relief.

Side effects are usually mild — spotting, bloating, tiredness, or mood changes. More serious risks depend on the drug and your health history. Always tell your provider about other medicines, migraines, blood clot history, or liver issues before starting hormone therapy.

If you want practical next steps: track your cycle for at least two months, save notes on symptoms, and bring that to your clinic visit. Ask for a mid-luteal progesterone test if you suspect anovulation. If a doctor recommends medication like Provera or a vaginal progesterone for fertility, ask how long to take it, what side effects to expect, and when they’ll recheck levels.

Want reading from the site? Check our posts on Provera, anovulatory cycles and PCOS, and what happens if you don’t ovulate for clear, practical guides tailored to these issues.