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Combination Oral Contraceptive (COC) Pills

Patient Education
Published April 17, 2020
• Reviewed by a UI Health Care Provider
on Feb. 9, 2026

What are COC pills? 

These are pills that have both estrogen and progestin. They are the most used “birth control pills.” 

  • COC prevents pregnancy 92 out of 100 times. This means in 1 year, 8 out of 100 people who use COC pills get pregnant.
  • COC does not protect against sexually transmitted infections (STIs). Use condoms with new partners.
  • Most COCs have 3 rows of hormonal pills and 1 row of placebo pills (do not have hormones).
    • Some have less than 7 placebo pills. 
    • Some have placebo pills every 3 months. 

What are the benefits of COC pills?

  • Patient controlled
  • More predictable periods. You know when your period may start.
  • Lighter and less painful periods
  • Lowers the chance of pregnancy
  • Less acne
  • Less risk of uterine and ovarian cancer when taken long term
  • Fewer symptoms of endometriosis and PMOS (polyendocrine metabolic ovarian syndrome)
  • Able to get pregnant right away after stopping. No impact on your ability to get pregnant in the future.

What are the risks of COC pills?

  • Getting pregnant.8 out of 100 people using COC will get pregnant each year while using them for contraception (preventing pregnancy).
  • There is a risk of blood clots in the legs or lungs.
    • For a person not taking any hormonal contraception and not pregnant, the risk of a blood clot is about 4 out of 10,000 people. 
    • For a person taking COC, the risk of a blood clot is about 6 to 10 out of 10,000 people.
    • The risk of a blood clot is higher while taking COC, but it is much less than during pregnancy. The risk of a blood clot is about 10 times higher in pregnancy than while on a birth control pill.

When can I start the pill?

  • COC can be started anytime if you are not pregnant. 
  • You do not need to wait for your next menstrual cycle (period). 
  • You do not need to wait until the Sunday after your period. 
  • If you have questions, talk with your care team about when to start your pill.

What if I am postpartum?

  • Your care team will tell you when you can start taking your COC pills after delivery. 
  • Most COCs are started 6 weeks after delivery. This is because of the risk of blood clots in the postpartum time. 
  • COCs are safe while breastfeeding and should not lower milk supply when started more than 6 weeks after delivery.

What if I had a miscarriage or abortion?

  • If you plan to use COC after a miscarriage or abortion, start the pills the first Sunday after the pregnancy passes. 
  • It is okay to start your pills even if you have vaginal bleeding at that time 

When does the pill start working? 

  • If the pill is started after the first 5 days of a regular period, it works right away.
  • If the pill is started any other time during a menstrual cycle:
    • Do not have sex for 7 days or use another birth control method (“back-up contraception”), such as condoms, for 7 days.
    • If you are switching from an IUD (intrauterine device), do not have sex or use a back-up birth control method for 7 days.
    • You do not need to use a back-up method if you switch from a non-IUD method, such as a pill, patch, ring, or shot.

How do I take the pill?

This depends on the type of pill you are taking.

Cyclic dosing

21-day pill packs

  • Take 1 pill at the same time each day for 21 days.
  • Wait 7 days before starting a new pack.
  • During the week you are not taking the pill, you will have your period.

28-day pill packs

  • Take 1 pill at the same time each day for 28 days.  
  • Depending on the brand, the first 21 or first 24 pills have estrogen and progestin.
  • The rest of the pills may be: 
    • Estrogen-only pills 
    • Pills with a dietary supplement, such as iron, but no hormones
    • Inactive pills that do not have hormones or supplements 
  • During the days you take the hormone-free pills, you will have your period.

90-day pill packs

  • Take 1 pill at the same time each day for 84 days.
  • Depending on the brand, the last 7 pills either have no hormones or have estrogen only.
  • With both brands, you will have a period during the last 7 days every 3 months.

Continuous dosing

  • If your care team prescribes a COC pill, take the active pills for 3 weeks.
  • Throw out the placebo pills. 
  • Start a new pack of pills right away.

What if I miss taking a pill or take it late?

If you are late taking a pill and it is less than 24 hours since you should have taken it

or

If you missed a pill and it has been 24 to 48 hours since you should have taken it:

  • Take the late or missed pill as soon as you can.
  • Keep taking the rest of the pills at the normal time, even if you must take 2 pills the same day.
  • There is no need for back-up contraception protection.

You often do not need emergency contraception (an over-the-counter pill sometimes called “the morning after pill”) if you missed hormonal pills early in your cycle or in the last week of your previous cycle. You may think about taking it though.

If you missed 2 or more pills in a row and it has been more than 48 hours since you last took a pill:

  • Take the most recent missed pill as soon as you can. Throw away the other missed pills.
  • Keep taking the rest of the pills at the normal time, even if you must take 2 pills in the same day.
  • Use back-up contraception, such as condoms, or do not have sex until you take your pills 7 days in a row.

If you missed pills the last week of your hormonal pills (days 15 to 21 for a 28-day pill pack): 

  • Skip the pills in the hormone-free week. Finish your hormone pills in your current pack. 
  • Start a new pack the next day.
  • If you cannot start a new pack right away, use back-up contraception, such as condoms, or do not have sex until you take your pills 7 days in a row.

You may want to take emergency contraception if you missed hormonal pills the first week in the pill pack and you had unprotected sex in the past 5 days. 

What if I keep forgetting to take my pill?

  • If you have a hard time remembering to take your birth control pill every day, you are not alone! This is common. 
  • There are other options for contraception where you do not need to take something  every day. Talk to your care team about those other options.

Where can I get more information if I missed a pill?

Go to the emergency room (ER) if you have: 

  • Eye problems, such as loss of eyesight or blurring
  • Problems talking
  • Severe headaches 
  • Dizziness 
  • Weakness 
  • Numbness
  • Shortness of breath or chest pain
  • Severe leg pain in 1 of your thighs or calves
  • Swelling in 1 leg (Swelling in both legs is not common if the swelling is caused by the COC pill.)

What are side effects of the pill?

Breakthrough bleeding

  • Light, irregular bleeding (spotting) is very common the first 3 months. This is more common with continuous pill use. It is not harmful.
  • If flow is light, keep taking the pills. Call your care team if you keep bleeding after the third cycle of pills. Ask about changing pills.
  • Call your care team if your flow is heavy. This means soaking more than 1 pad in 1 hour.

Nausea (feeling sick to your stomach)

  • This is common the first 2 to 3 months. Try taking the pill at bedtime or on a full stomach.

Headaches

  • This is common the first 2 to 3 months. Keep track of how severe and often you have them.
  • Try over-the-counter pain medicine, such as naproxen sodium, ibuprofen (Advil®), or acetaminophen (Tylenol®).   

Weight gain

  • There is no evidence COCs cause weight gain.   
  • You may have some fluid retention. It should be less than 5 pounds.

No period during placebo pills

  • If you have not missed any pills, this may be normal. Take a home pregnancy test if you think you might be pregnant. If the test is negative, keep taking the pills.

Who do I call if I have questions or concerns? 

  • Call the Obstetrics Gynecology Clinic at 319-356-2294, Monday through Friday from 8:00 a.m. to 4:30 p.m.  
  • For urgent questions or concerns:
    • Call toll-free at 800-777-8442, 24 hours a day
    • Ask for the gynecology resident on call.
    • You may be asked some questions when using the toll-free number.

Send a MyChart message for non-urgent questions or concerns.