How Do Oral Contraceptives Work?

Reviewed on 12/27/2021

How do oral contraceptives work?

Oral contraceptives, also known as birth control pills, are hormonal medications taken before and/or after vaginal intercourse to prevent pregnancy. Oral contraceptives work by interfering with a woman’s natural hormonal balance that enables ovulation, egg fertilization, implantation, and maintenance of pregnancy.

Oral contraceptives are formulations of only progestin or a combination of progestin and estrogen. Oral contraceptives are synthetic forms of the natural female sex hormones progesterone and estrogen and have similar effects. Some oral contraceptives contain iron to supplement the body’s needs, in case of insufficiency.

Oral contraceptives bind to progesterone and estrogen receptors, protein molecules in cells that respond to these hormones, and disrupt the hormonal balance to prevent pregnancy. Oral contraceptives work in the following ways:

How are oral contraceptives used?

Oral contraceptives are tablets of varying formulations of progestin-only or progestin/estrogen combination, taken one a day at the same time every day, starting on the first day of menstruation. Oral contraceptives are available in packs of different cycles such as:

  • 21-day cycles: Taken in 21-day cycles with seven no-pill days during which time menstruation will occur.
  • 28-day cycles: Taken in 28-day cycles with hormonally active pills for 21 days and inert pills for seven days. Having no gap in ingestion makes compliance easier.
  • 91-day cycles: Taken in 91-day cycles with active pills for 84 days and estrogen-only or inert pills for seven days. Menstruation occurs only once in three months.
  • Yearly cycle: Continuous ingestion of low dose pills every day for a year or longer. Periods may get lighter or stop altogether during the period it is followed.

Most oral contraceptives are taken every day in cycles during the period birth control is followed. In case of unprotected vaginal intercourse or a known or suspected contraceptive failure, emergency birth control tablets can be taken. Post-intercourse tablets are taken just once and must be taken as early as possible within 72 hours after, to be effective.

Oral contraceptives may not be suitable for women over the age of 35 who smoke or have certain health conditions such as cardiovascular diseases or diabetes mellitus. The uses of oral contraceptives include:


Off-label uses:


Choosing Your Birth Control Method See Slideshow

What are side effects of oral contraceptives?

Side effects of oral contraceptives may include the following:

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with travel medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

What are names of oral contraceptive drugs?

Generic and brand names of oral contraceptive drugs include:


Which of the following are methods for contraception? See Answer

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