Women's Health

How does birth control work?

How do various hormonal birth control options help prevent pregnancy? Our experts help you understand the details so you can make the best choice for you.
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Key Points:

  1. Hormonal birth control methods can prevent ovulation, make it harder for sperm to reach an egg and make it harder for a fertilized egg to implant.
  2. Hormonal birth control options include pills, rings, implants, patches, injections and intrauterine devices (IUDs).
  3. These forms of birth control do not protect against sexually transmitted infections (STIs). Using a barrier method like condoms is the best way to prevent STIs.

If you want to prevent pregnancy, birth control treatment can provide peace of mind.

Depending on the method you use, it may also relieve symptoms of other health conditions or result in lighter periods. That’s why it helps to know how each method works before you choose a new or different form of contraception. Read on for the nitty gritty.

And if you’re ready to get a birth control prescription online? Start a discreet $15 consultation with Dr. B. A licensed provider can help you choose the best option for you.

How does hormonal birth control work?

First off, here’s how pregnancy happens: Each month, the ovaries release an egg (a process called ovulation). Once in the fallopian tubes, sperm can fertilize the egg and travel down to the uterus, where it implants and starts to develop. When it comes to preventing this process, barrier and hormonal types of birth control work differently.

Barrier methods (like condoms) prevent pregnancy by stopping sperm from entering the uterus. Hormonal methods use hormones (like progesterone and estrogen) to stop ovulation or change the body in ways that make pregnancy less likely. Depending on the hormones they contain, they may:

  • Stop ovulation: Without an egg, you can’t get pregnant. 
  • Thin the uterine lining: This makes it harder for a fertilized egg to implant. 
  • Thicken cervical mucus: This makes it more difficult for sperm to enter.

When taken correctly, most birth control is over 99% effective at preventing pregnancy. But each comes with its own benefits and side effects. So let’s dig deeper into how hormonal methods like the pill, patch, ring and implant work.

​​How birth control pills work

Birth control pills contain one or several hormones to prevent pregnancy.

Combination pills include forms of both estrogen and progesterone. The minipill only contains progestin—a form of progesterone. This option may be better for people who are breastfeeding, who have a history of blood clots or strokes or who shouldn’t take estrogen for other reasons.

When taken correctly, birth control pills are more than 99% effective. But many people find it difficult to remember to take the pill at the same time every day, which keeps hormone levels in the body constant. If you miss a day or take the pill at different times, it’s possible to get pregnant. Because of this, 9 out of 100 people on the pill become pregnant yearly.

How the birth control patch works

The birth control patch is a combination medication that’s put on the skin, where it remains for three weeks. It’s then removed for one patch-free week before being replaced with a new patch.

Because it only needs to be changed once a month, the patch can be easier to use than the pill. It’s also 99.7% effective when used perfectly. But real-life studies show that 9% of people who use the patch become pregnant every year.

How the birth control ring works

The birth control ring is a small, flexible ring placed in the vagina. It contains forms of progesterone and estrogen that release into vaginal tissue. This stops ovulation and changes the uterus and cervix, making pregnancy less likely.

The ring is left in place for three weeks and then removed. Some people leave it out for up to 7 days before replacing it. Others immediately put in a new ring to prevent a menstrual cycle (your period).

Like the patch and the pill, the ring is 99.7% effective at preventing pregnancy when used perfectly and 91% effective according to typical use.

How birth control implants work

The birth control implant contains a form of progesterone called etonogestrel, which tells the pituitary gland not to release an egg. Like the pill, it also thickens the mucus of the cervix, which makes it harder for sperm to pass through and enter the uterus.

The implant is placed by a healthcare provider under the skin of the upper arm, where it can stay for up to three years. Since this removes human error, it is more than 99% effective at preventing pregnancy.

Hormonal birth control and STIs

Hormonal birth control cannot prevent STIs. People with more than one partner, those at high risk of STIs or anyone wanting to maximize their contraception should use both hormonal and barrier methods.

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How Dr. B can help you get birth control online

With so many options available, choosing the right birth control can be difficult. Fortunately, you can access birth control online with a little help from Dr. B.

Start a discreet $15 online consultation—no video call required. A licensed provider will review your treatment and help you choose the best birth control option. We’ll also show you the lowest possible medication costs at your local pharmacies and send you a drug discount card to secure that price.

The process is private and confidential—and it’s available whether or not you have insurance.


American College of Obstetricians and Gynecologists. Progestin-only hormonal birth control: Pill and injection.

American Society of Health-System Pharmacists, Inc. Progestin-only (Norethindrone) oral contraceptives.

Britton, L. E., et al. (2020). CE: an evidence-based update on contraception. The American Journal of Nursing.

Cooper, D. B., et al. (2022). Oral contraceptive pills. StatPearls.

Horvath, S., et al. (2018). Contraception. Endotext.

Planned Parenthood. Birth control implants: NEXPLANON information.

Planned Parenthood. Birth control patch: Ortho Evra: transdermal patch.

Planned Parenthood. Nuvaring: birth control vaginal ring: estrogen ring.

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