Progestin-Only Pills

What are Progestin-only Pills?

The progestin-only pill, also known as the “mini pill,” contains the hormone progestin and, unlike the combination pill, does not contain estrogen. One monthly pack contains 28 “active” pills without a week of placebo or “inactive” pills; every pill contains a small dose of progestin.4

How they Work

The pill prevents pregnancy in several ways:

  • Thickens the cervical mucus, which physically prevents sperm from entering the uterus and fallopian tubes to fertilize an egg.
  • Thins the lining of the uterus, making it difficult for a fertilized egg to implant itself.
  • Suppresses ovulation (prevents the discharge of an egg from the ovaries into the fallopian tubes).4

How they Should Be Taken

Progestin-only pills must be taken at the same time every day. These pills are almost immediately reversible: it only takes about 24 hours for the small amount of ingested progestin to leave the body.5 If each pill is not taken at the correct time, the cervical mucus will become thinner, and sperm will be able to pass through the cervix.1 If you take the pill more than three hours later than the usual time, a back-up birth control method (such as a condom) should be used for at least two days. Breaks should not be taken between pill packs. Some medications, including antibiotics, anti-HIV medication, and drugs that prevent seizures, will interfere with the mini pill. Be sure to use a back-up method while taking these medications, and talk to your doctor about their potential effect on your birth control regime.4

You can start taking the pill at any time, as long as you are not pregnant (do not start taking the pill if you think you may be pregnant).4 If you start a new pack on the first day of your menstrual period, the pill will begin working within 48 hours, so it is best to use a back-up method during those first two days.2 If you start taking the pill at any other time during your menstrual cycle, it is recommended that you abstain from sexual intercourse or use a back-up contraceptive for the first seven days after starting the pill.1 If you switch from the “combo pill” to the progestin-only pill, start taking the progestin-only pack on the day after you take your last active combination pill.4

What to do if You Miss a Pill:

  • If you miss one pill, take it as soon as you remember and continue taking the rest of your pills at the usual time. You may have to take two pills in one day.3
  • If you miss two or more pills in a row, take two pills a day for two days.3
  • Abstain from sex or use a back-up method of birth control for 2-7 days after you miss any pills.1
  •  If you have unprotected sex after missing any number of pills, consider using emergency contraception. If your period has not arrived within 4-6 weeks, a pregnancy test should be taken.5

Vaginal bleeding or spotting after missing pills is common, but you should not stop taking the pill if you experience this.1

Progestin-only Pill vs. Combination pill

Progestin-only pills are often recommended to women who…

  • are breast-feeding. The estrogen in the combination pill interferes with milk production.4
  • smoke cigarettes, are older than 35, or have health problems like heart disease, blood clots, high blood pressure, and migraines. The lack of estrogen in progestin-only pills makes them less likely to cause blood clots.1
  • do not want the side effects of estrogen in combination pills (side effects include risk for blood clots, nausea, weight gain, breast enlargement).4

Effectiveness of Progestin-only Pills

When used consistently, exactly as directed (perfect use), less than 1 in 100 women will become pregnant in the first year of use. With typical use (inconsistently or as used by the average female), the progestin only pill is 91% effective, meaning that 9 out of 100 women will become pregnant in the first year of use.2 These pills are typically less effective than the combo pill.4


Advantages of the Progestin-only Pill

  • Lighter bleeding, less cramping and PMS5
  • Decreased risk of uterine and ovarian cancer5
  • If you do become pregnant while taking the pill, the fetus will not be harmed by the small amount of progestin in the pill5
  • The pill can reduce iron-deficiency anemia4
  • Immediately reversible if pregnancy is desired5

Disadvantages and Risks

  • You must remember take the pill every day at the same time, requires regularity
  • May be less effective than the combo pill4
  • If you become pregnant, it can be difficult to recognize the symptoms; there is a higher chance of ectopic pregnancy4
  • About one half of women taking the progestin only pill experience irregular menstrual bleeding and spotting between periods5
  • Other side effects include acne, breast tenderness, decreased libido, mood changes, depression, headaches, nausea, ovarian cysts, and weight gain. Do not stop taking the pill if you experience these side effects. Consult your doctor if your side effects are concerning1
  • The pill does NOT protect against sexually transmitted infections. Condoms should be used to reduce the risk of spreading or contracting STIs4

Abnormal Symptoms

Severe stomach or abdominal pain, chest pain, shortness of breath, coughing up blood, persistent headaches, vision changes, loss of sensation in any body parts, and calf or thigh pain that makes it hard to walk are all abnormal symptoms of the pill and should be reported to your doctor.1 Also consult your doctor if your period is more than 45 days late.5

For more information regarding various methods of contraception, click here!



1.     "Birth Control Pills - Progestin-Only Contraceptives." N.p., n.d. Web. 23 Jan. 2014.

2.     "Birth Control Pills." Planned

Parenthood, n.d. Web. 21 Jan. 2014. 

3.     "The "Mini-Pill" or Progestin-Only Contraceptive." McKinley Health Center, University of Illinois, n.d. Web. 23 Jan. 2014. 

4.     "Minipill (progestin-only Birth Control Pill)." N.p., n.d. Web. 23 Jan. 2014. 

5.     "Progestin-only Pills (POPs)." Sexual Health Services and Support for BC. N.p., n.d. Web. 23 Jan. 2014.

Last Updated 26 January 2014.