Progestin-Only Pills

Contraceptive pills in blue packaging.

The progestin-only pill, also known as the “mini pill,” is a type of oral contraceptive, or oral birth control pill. The pill contains the hormone progestin and, unlike the combination pill, does not contain estrogen. Due to this lack of estrogen, many users report feeling fewer side effects. One monthly pack of progestin-only pills contains 28 “active” pills, which each contain a small dose of progestin, unlike the combination pill which contains a week of placebo or “inactive” pills.4 The progestin-only pill, if used correctly, is a highly effective way of preventing pregnancy, though it does not protect against sexually transmitted infections.

How they Work

The progestin-only pill prevents pregnancy mainly by changing the physical and chemical environment of the female reproductive tract. In this new environment, it is more difficult for fertilization to occur: the progestin causes the cervical mucus to thicken, which physically prevents sperm from entering the uterus and fallopian tubes to fertilize an egg. Additionally, the progestin thins the lining of the uterus, making it difficult for a fertilized egg to implant itself. It also suppresses ovulation (prevents the discharge of an egg from the ovaries into the fallopian tubes) as it makes your body “think” that you are pregant.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 of birth control while taking these medications, and talk to your doctor about their potential effect on your birth control regimen.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:

Contraceptive pills in blue packaging.

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 as the estrogen in the combination pill interferes with milk production.4 They are also often recommended to females who smoke cigarettes, are older than 35, or have health problems like heart disease, blood clots, high blood pressure, and migraines. Progestin-only pills are safer for these individuals because they are less likely to cause blood clots.1 Females who do not want the side effects caused by the estrogen in combination pills (side effects include risk for blood clots, nausea, weight gain, breast enlargement) are also often recommended to take the progestin-only pill.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 the rate of imperfect use (typical use), 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 combination pill.4 Due to the fact that most women are “typical users,” it is recommended to combine oral contraceptives with the male or female condom to best ensure the prevention of pregnancy as well as sexually transmitted diseases.

Advantages of the Progestin-only Pill

A bunch of white pills.

In addition to avoiding potential side effects of estrogen in combination birth control pills, there are also other advantages of the progestin-only pill. These advantages include:

  • 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
  • May reduce iron-deficiency anemia4
  • Immediately reversible if pregnancy is desired5

There are many advantages of the progestin-only pill that make it a viable and attractive birth control option for many females.

Disadvantages and Risks

As with most methods of birth control, the progestin-only pill also has potential side effects and drawbacks.

A variety of fruits and vegetables: bell pepper, eggplant, banana, and cucumber,  wrapped in condoms.
  • You must remember take the pill every day at the same time
  • May be less effective than the combination pill4
  • If you become pregnant, it can be difficult to recognize the symptoms; there is also 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. 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

When choosing the method of birth control that is right for you, it is important to consider both the advantages and disadvantages of each method.

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 part, and severe calf or thigh pain are all abnormal symptoms of the pill and should be reported to your doctor.1 Consult your doctor if your period is more than 45 days late.5

Concluding Remarks

The progestin-only birth control pill, when used correctly, offers women a reliable way to prevent pregnancy. It also allows users to avoid the potential side effects of estrogen, a hormone found in the combination pill. The progestin-only pill must be taken consistently at the same time every day for maximized efficiency. There is no contraceptive method that is perfect for everyone, but with such a wide variety of choices available, you can find one that works best for you. Consult a doctor to discuss the best birth control options for you and your body. 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: 07 February 2019.