University Health Service

birth control pill pack

What are birth control pills?

Birth control pills, also called oral contraceptives or “the pill,” are taken daily to prevent pregnancy.

There are two categories of pills:

  • Combination pills contain the hormones estrogen and progestin; most users take these
  • Mini-pills contain only progestin and may be a good option for users who cannot use estrogen

How do they work?

Birth control pills have hormones, either estrogen and progestin, or progestin only. These hormones prevent ovaries from releasing eggs and/or prevent sperm from fertilizing an egg.

How effective are birth control pills?

9 out of 100 users will get pregnant each year. 

The pill may be less effective for users who are overweight. Also, certain medications and supplements may make the pill less effective. Vomiting and diarrhea may also keep the pill from being completely protective from pregnancy. Talk to your health care provider for advice about which birth control method suits you.

What are the benefits?

  • Birth control pills are an effective, safe and convenient method to prevent pregnancy.
  • You do not have to think about birth control every time you have sex.
  • Users can get pregnant shortly after they stop using the pill.
  • Menstrual cramps may be reduced and your periods may become lighter while using the pill.
  • The hormones in combination birth control pills offer some additional benefits, including:
    • Some protection against acne, anemia, PMS, migraine headaches, non-cancerous breast growths, ectopic pregnancy, endometrial and ovarian cancers, ovarian cysts and pelvic inflammatory disease.
    • May be used to control when and how often you have your period.

What are the downsides?

  • It is not always easy for users to remember to take the pill every day or at a particular time of the day. You may need to use a back-up birth control method or take emergency contraception if you miss a pill or take it too late. 
  • You will need to visit a health care provider annually for a new prescription.  
  • You will need to remember to refill your prescription regularly.
  • Birth control pills do not provide protection from sexually transmitted infections (STI). Male condoms or female condoms can be used to prevent STI.
  • Some users have side effects which may include bleeding between periods, breast tenderness, nausea, and vomiting. Do not stop taking the pill if you have nausea because you will be at risk for pregnancy. These common side effects typically go away after two or three months of use. If you experience nausea, avoid taking the pill on an empty stomach. 
  • Some users experience a change in their sexual desire from the hormones in the pill.

What are the health risks?

The pill is safe for most users. Methods containing estrogen and progesterone have a greater risk of certain problems including heart attack, stroke, blood clots, or developing high blood pressure, liver tumors, gallstones, or yellowing of the skin or eyes (jaundice). The risk increases if you smoke, are age 35 or older, are very overweight, have certain inherited blood-clotting disorders, have diabetes, have high blood pressure, have high cholesterol, or need prolonged bed rest. People with certain health risks should not use combination pills. 

Where can I get them and what are costs?

You can get a prescription for birth control pills from a UHS health care provider, and you can purchase them at the UHS Pharmacy or another pharmacy. Request prescription refills directly through your pharmacy. If your prescription has expired, you will need to schedule an appointment by calling 734-764-830 or see How to Get Health Care.  See also Cost, Insurance and Payment.

How do I use them?

Timing is important. You must choose a consistent time of day that works for you to take the pill.

With combination pills:

  • If you are more than three hours late in taking your pill, you may have break-through bleeding, and effectiveness may decrease.

With mini-pills:

  • If you are 15 minutes late in taking your pill, you may experience break-through bleeding.
  • If you are 3 hours late, you need to use a back-up method of birth control for two days after taking that missed pill.

Combination pills come in packs of 21, 28 and 91 pills.

  • All packs contain active pills with hormones.
  • Some packs contain inactive placebo pills -- they do not contain hormones but simply serve as a reminder, and they may be a different color from the active pills.

21-day packs have 21 active pills and no inactive pills. You will take one pill every day for three weeks. No pills will be taken for the next seven days and your period will begin, unless you choose to avoid your period by starting a new pack of active pills. The next week, you will begin a new pack of pills.

28-day packs have 21 active pills and 7 inactive pills. You will take one pill every day. You will menstruate during this week of inactive pills, unless you choose to avoid your period by starting a new pack of active pills.

91-day packs have 84 active pills and 7 non-active reminder pills. You will take one pill every day. You will menstruate during this week of inactive pills, unless you choose to avoid your period by starting a new pack of active pills. These 91-day packs are meant to reduce the number of periods that users have throughout the year.

Users may also take the active pills in 21-day or 28-day packs during the fourth week or continuously to reduce how often they have periods. Not all pills can be used this way. Talk to your health care provider if you'd like to use pills to modify your period. 

Mini-pills come only in 28-day packs. All the pills in these packs are active. You will take one mini-pill every day for the entire month, and you may get your period in the fourth week of the month. You many also have no periods or have occasional bleeding throughout the month.

How to start taking birth control pills

You may start the pill on any day of the month. Talk to your health care provider to choose what day is best for you to start.

Combination pills: If you start combination pills within five days after the start of your period, you will prevent pregnancy right away and do not need to use a back-up method of birth control. If you start taking the pill at any other time throughout your menstrual cycle, you will need to use another method of birth control for the first seven days.

Mini-pills: You should use another method of birth control during the first 48 hours of use, after which you will be protected from pregnancy. Remember that taking the mini-pill at the same time each day is essential to prevent pregnancy.

Important tips

  • Certain side effects from using the pill, such as nausea and vomiting, may be helped by taking the pill in the evening or with food.
  • Remind yourself to take your pill e.g. set an alarm on your phone or watch, use an app, or pick a consistent time of the day that is easy for you to remember to take the pill. 
  • It's not unusual for users to miss a period while taking the pill. You should take a pregnancy test if you miss two or three periods in a row. 

Personal experiences

I like taking the pill because it regulates my period (in terms of having a period every month and keeping it lighter than it often is without the pill), in addition to preventing pregnancy. I have been taking birth control for over five years, but I have tried about six different kinds. Some of them altered my mood (i.e., made me feel super down) or made my stomach hurt, so it took some time for me to find the one that works for me.

Not only did it make my period lighter, get rid of my acne, and stop my cramps, it makes me feel much more confident that I will not become pregnant! I have an alarm set on my phone for 8 PM each night that reminds me to take it and I try to keep my pack of pills with me in my purse so that I always have it.

I began taking the oral birth control pill when I became sexually active at age 17. I began having chronic and severe migraine headaches. At that time, I experienced an unintended pregnancy and immediately switched to an IUD. I am now happy with Mirena, which has meant more effective birth control and fewer migraines.

Where can I get more information?

Talk to your health care provider. You can also get reliable information from the following websites: