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Cyclic Progesterone Therapy

Why Might I Need To Take Cyclic Progesterone Therapy?

Progesterone is one of two important women's hormones; estrogen is the one we usually hear about. When menstrual cycle length is irregular or cycles are long or skipped, or when egg release is absent despite regular cycles, progesterone levels are low or missing.

Your doctor may prescribe progesterone or a synthetic called medroxyprogesterone (MPA), to control heavy flow, prevent irregular periods, acne, unwanted hair, or treat low bone density, or for perimenopausal sore breasts, sleep problems, heavy flow or night sweats. Cyclic progesterone therapy (not MPA) also helps women achieve pregnancy.

What Medications Can I Choose? 

Oral micronized progesterone (Prometrium® or the same hormone "compounded" in oil by a pharmacist) is identical to your own hormone (or bio-identical). Because it may cause sleepiness, only take this medication on your way to bed. Three 100 mg. capsules is the dose that keeps progesterone levels in the normal range for 24 hours—it costs *$5.50 a day.

Medroxyprogesterone (MPA) is synthetic or progestin that has been used for over 40 years. As a pill it does not provide contraception like DepoMPA, and doesn't have the same side effects while on it or difficulties when stopping it. It is stronger than progesterone so the dose that creates a progesterone-like effect is 10 mg. a day. A one-day dose costs about *Canadian $0.36.

When Do I Take It?

The first day of menstruation is called "day 1." If you get a period regularly and your cycles are usually 27-30+ days long, start progesterone on the 14th day after flow began and take it for 14 days or until cycle day 27. If your cycles are regular but shorter (for example, if your period starts every 21–26 days), then start cyclic progesterone/MPA on cycle day 12 and continue it for 14 days or until cycle day 25.


Diagram 1 

If your period starts before you have finished the 14 days of progesterone/MPA, finish the full 14 days, but start the next progesterone 14 days after the flow began. This allows for a "catch up" with your own (likely high) estrogen levels.


Diagram 2

If your period starts while you are still taking progesterone/MPA, always take it for the full 14 days.

If this early flow persists, or you are in perimenopause, then you either need daily progesterone/MPA for three months or to increase the dose of cyclic therapy to 400 mg progesterone or 20 mg MPA. The early flow is a sign that your body is making high levels of estrogen that are over-stimulating the endometrium (uterus lining) and causing heavy bleeding.

If you have not started to flow within two weeks of taking cyclic progesterone/MPA, it means your own estrogen levels are low. Stop progesterone for 14 days. After 14-days "off," start the next progesterone cycle.

As soon as your flow returns, then start taking progesterone/MPA again, 14 days after the start of your flow, as shown in Diagram 1.

Are There Any Side Effects?

There are no serious negative effects from progesterone therapy—the most important is improved sleep! It does not cause blood clots, migraine headaches or increase the risk for breast cancer. In a dose of 300 mg for 14 days, it effectively prevents endometrial cancer. Pharmacy references say that progesterone causes everything shown on "the Pill" (combined hormonal contraceptives) which contain 4 times normal estrogen doses plus synthetic progestins. Prometrium® is in peanut oil; therefore those with peanut allergy must NOT take it. With MPA the major concerns are that it increases breast cancer risk in menopausal women taking estrogen therapy and should be avoided if possible when seeking pregnancy.

You may notice some changes in your breasts, feelings of warmth and other evidences of normal progesterone action. If you get moody, feel bloated and have very sore breasts it means progesterone is temporarily stimulating your body to make higher estrogen levels. This improves after one cycle.

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Dr. Jerilynn C. Prior, Scientific Director, Centre for Menstrual Cycle and Ovulation Research
Updated Date: 
November 28, 2014

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