What Are the Hormones in Hormonal Birth Control?

Most people have an idea of how hormonal birth control works—hormones are released into the body from a pill (or a patch, or a shot, or a vaginal ring), and these hormones help prevent pregnancy.

The best-known example of hormonal birth control is the birth control pill. There is a good reason for this—the first contraceptive pill became available in 1960 and pills are the most commonly prescribed contraceptive in the United States.

But what hormones do these contraceptives contain? How exactly do they help prevent pregnancy? And how do you decide if you should use a hormonal or non-hormonal method (or both)?

For answers to these questions and more, keep reading!

The hormones in hormonal contraceptives
Hormonal contraceptives contain lab-made versions of the hormone progesterone, called progestin. Some birth control methods contain a combination of progestin plus a lab-made version of the hormone estrogen. These hormones prevent pregnancy in three different ways:

• Stopping the ovary from releasing an egg, which means there is no egg in the womb for sperm to fertilize.
• Thickening cervical mucus, which creates a sticky barrier that makes it difficult for sperm to reach the womb.
• Preventing the lining of the uterus from thickening. This makes it difficult for a fertilized egg to implant in the uterus. This is also the reason why people taking continuous hormonal birth control do not have menstrual periods but may experience withdrawal bleeding (both occur as a result of a drop in hormone levels).

Keep in mind that this is an overview of how hormonal birth control works, and there is much more nuance once you start delving into specific brands. For example, birth control pills can be further categorized depending on how many active pills come in a pack (which can range from 21 to 84) and whether the dosage of hormones in each pill is the same, or whether it varies during the month.

Hormonal birth control and side effects
Hormonal birth control is generally safe for most people and—used correctly—is very effective at preventing unplanned pregnancy. It’s also worth noting that hormonal contraceptives may be prescribed for other reasons—regulating an irregular menstrual cycle, or treating conditions like heavy and painful periods, menstrual migraines, and endometriosis.

But—as with any medication—there is a risk of side effects. And hormonal birth control should not be used by people with a history of certain medical conditions, including migraine headaches, liver disease, cardiovascular disease, breast cancer, and certain other cancers.

If you're unsure about taking hormonal birth control or what hormonal birth control is best for you, talk to your healthcare provider, who will be your best source of information.

Medically reviewed in April 2021.

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