Progesterone — what it does and when you might need it

Progesterone is a natural hormone most people know about from pregnancy and menstrual cycles. It helps prepare the uterus for pregnancy, supports early pregnancy, and balances estrogen. Doctors prescribe progesterone for several conditions: irregular periods, luteal phase defects, assisted reproduction support, and as part of hormone replacement therapy (HRT) for menopausal symptoms.

There are two main categories: bioidentical progesterone (the same molecule your body makes) and synthetic progestins (similar but chemically different). Bioidentical forms often come as oral capsules, vaginal gels or suppositories, and topical creams. Progestins are used in many birth control pills and some HRT regimens. The choice depends on the condition being treated, side effect profile, and what your clinician prefers.

How it’s used in practice

For fertility care, progesterone is commonly given after ovulation or embryo transfer to support the uterine lining. In HRT, progesterone is added when estrogen is used by a woman with a uterus to reduce the risk of endometrial hyperplasia. Doses vary: fertility protocols might use micronized progesterone 100–400 mg daily (often vaginal), while HRT doses are usually lower. Always follow the exact dose and route your provider prescribes.

Side effects, risks, and monitoring

Common side effects include tiredness, breast tenderness, bloating, mood changes, and spotting. These often settle after a few weeks. More serious but rarer risks include blood clots (especially when combined with estrogen), changes in liver enzymes, and allergic reactions. If you have a history of thrombosis, stroke, or certain cancers, tell your doctor before starting progesterone.

Monitoring usually means a medical history, blood pressure checks, and symptom review. If you’re on long-term HRT, your clinician may recommend periodic check-ups and cancer screening appropriate for your age.

Drug interactions matter. Some antifungals, antibiotics, and seizure medications can change progesterone levels. If you take other medicines, list them for your prescriber and ask whether interactions are likely.

Buying progesterone online can be tempting, but be cautious. Use licensed pharmacies, check for verified seals, and never use a product without a prescription when one is required. Counterfeit or poorly stored hormones can be ineffective or unsafe. If cost or access is an issue, ask your provider about generics or patient assistance programs.

Quick practical tips: take oral progesterone at bedtime if it causes sleepiness, follow vaginal protocols exactly (don’t skip doses before embryo transfer), and report severe mood shifts or signs of clotting (sudden leg pain, shortness of breath) immediately. If you plan pregnancy or are breastfeeding, discuss timing and safety with your clinician.

If you want more on progesterone-related topics—dosing for fertility, comparing bioidentical vs synthetic, or how progesterone interacts with other meds—check our related guides or ask a pharmacist or specialist for advice tailored to your situation.