Progesterone is a hormone that regulates the menstrual cycle and supports early pregnancy. Its primary function is to prepare the uterine lining (endometrium) for potential implantation by thickening it and increasing blood supply. Since progesterone is used for several medical purposes, whether you should stop taking it when bleeding starts depends entirely on the reason it was prescribed. Always consult your prescribing physician or healthcare provider before making any changes to your medication regimen.
Progesterone for Luteal Phase Support and Fertility
Progesterone is prescribed to support the luteal phase, particularly during in vitro fertilization (IVF), intrauterine insemination (IUI), or for women with recurrent miscarriage. This supplementation helps stabilize the uterine lining, which is necessary for successful embryo implantation and maintaining an early pregnancy. In this context, any bleeding, whether light spotting or a heavier flow, requires immediate communication with your fertility clinic.
If you experience bleeding before your scheduled pregnancy test, you must continue the medication as directed; stopping prematurely could compromise an otherwise healthy pregnancy. Progesterone levels are crucial in the first trimester, until the placenta fully develops and takes over hormone production, which occurs around 10 to 12 weeks of gestation. The instruction to continue the medication holds even if you believe the bleeding is your period, as the medication can mask or delay the onset of menstruation.
If the blood test confirms pregnancy, your doctor will likely advise you to continue progesterone for several more weeks. If the test is negative, you will be instructed to stop the supplementation. The resulting drop in hormone levels will then trigger a menstrual period, usually beginning within two to five days after the last dose.
Progesterone as Part of Hormone Replacement Therapy
For women using sequential combined hormone replacement therapy (HRT) during perimenopause or post-menopause, progesterone is taken alongside estrogen to protect the uterus. Estrogen encourages the thickening of the uterine lining, and the cyclic administration of progesterone for 10 to 14 days each month ensures this lining sheds. This shedding prevents an overgrowth of the endometrium, reducing the risk of endometrial hyperplasia or cancer.
The bleeding that occurs after completing the progesterone course is a planned event known as a withdrawal bleed, not a natural period. When the withdrawal bleed starts, the standard instruction is to stop the progesterone component of the regimen. You will then restart the progesterone on a designated day of the next month, as per your doctor’s specific schedule.
Unscheduled bleeding that happens outside of the expected withdrawal window is known as breakthrough bleeding. This is common during the first three to six months of starting or adjusting HRT as your body adapts to the new hormone levels. Bleeding that persists or starts unexpectedly after six months of consistent HRT use should be reported to your healthcare provider for evaluation.
Progesterone Used to Induce a Withdrawal Bleed
Progesterone may be prescribed for a short duration (often five to ten days) specifically to trigger a period in women with amenorrhea (lack of menstruation). This course builds up the uterine lining, which has not shed due to a lack of progesterone. The goal is to simulate a normal cycle and force a bleed.
The onset of bleeding signifies that the medication has achieved its purpose. The bleeding is caused by the sudden drop in hormone levels after the full course of pills is completed. Therefore, you must finish the prescribed number of days of medication; the period will follow shortly after the last dose.
Warning Signs and When to Contact Your Provider
Regardless of the reason for your progesterone prescription, certain symptoms warrant immediate medical attention. Any sudden, severe, or unexpected change in your bleeding pattern should be reported to your provider. This includes bleeding that is significantly heavier than a normal period or that contains large blood clots.
Other symptoms requiring emergency contact include signs of a potential blood clot or severe complications. These include:
- Sudden and severe headache
- Pain or swelling in the leg
- Slurred speech or sudden vision changes
- Severe abdominal or pelvic pain
- Fever
- Bleeding that continues for an extended time outside of a scheduled window