Birth control pills are 98% to 99% effective for users who take the pills every day as directed. Pill taking mistakes decrease effectiveness and, because of user error, the typical effectiveness of pills in the first year of use is 91%. There are detailed instructions on late or missed pills below.

Birth control pills do not offer any protection against sexually transmitted infections (STIs). We recommend using condoms with birth control pills to protect against sexually transmitted infections. 

Like all medicines, birth control pills have possible side effects that you need to be aware of. There are minor side effects and also rare but serious side effects. 

Minor side effects of BCPs:

• Nausea

  • Some users experience some mild nausea when first starting birth control pills. Usually this goes away within a short time. Taking your pill with food or taking it before bedtime may help. If you have persistent problems or unusually severe nausea, contact your provider.

• Breast tenderness or enlargement

  • Mild breast tenderness or enlargement may occur after starting birth control pills. The tenderness can be reduced by decreasing your caffeine and salt intake and by wearing a bra with good support. Usually it gets better within a few weeks. If you notice persistent discomfort or a discrete lump, make an appointment with your provider.

• Headaches

  • If you develop new headaches while on birth control pills, contact your provider.

• Spotting or breakthrough bleeding

  • This is vaginal bleeding that occurs during your active pills. This is a common side effect during the first 3 months of birth control pills use and up to 50% of users may experience this. By the third pack of pills, 90% of users are no longer experiencing spotting. Some may notice some mild menstrual cramping with the spotting but this should resolve for most by the third pack of pills as well. Contraceptive effectiveness is present even with spotting, as long as no pills have been missed.

  • If you are experiencing light bleeding on your active pills that lasts longer than 5 days, or heavier bleeding lasting more than 3 days, contact your provider.

• Missed periods or amenorrhea

  • Sometimes a user may take all her pills correctly and will not get a period. This can happen for a variety of reasons including stress, illness and travel and, rarely, thyroid or other hormonal issues. A pregnancy test would be advised before starting a new pack of pills. If you have missed pills and don't get your period, or your period is very light, it is particularly important to take a pregnancy test.

  • If you continue to experience amenorrhea (absence of your period), contact your provider. A change to another birth control pill can help.

• Weight gain

  • Many patients ask about this side effect. Studies have shown that weight changes in people on birth control pills are no different than among people who don't take birth control pills. 3 placebo-controlled randomized clinical studies have demonstrated birth control pills do not cause weight changes. However, some users may react to the hormones with mild fluid retention in some tissue around the breasts and hips.

• Mood changes

  • Some users may notice changes in their emotional status: depressed mood or emotional instability. If you have a history of depression, discuss this with your provider. It is important to monitor your progress carefully when starting birth control pills. If you notice changes in your mood after beginning birth control pills, promptly contact your provider.

• Decreased sex drive

  • While your sex drive is affected by many things, the hormones in birth control pills can be a factor in decreased sex drive. If you are noticing this side effect persistently, let your provider know. A change to another pill or another method of contraception may be considered.

• Vaginal discharge

  • A slight increase in the amount of discharge can occur for some users. Others may notice decreased lubrication with intercourse. Neither change is harmful and added lubrication can be used as needed to make sex comfortable.

• Contact lens use

  • Rarely, users who wear contacts may notice some visual changes or change in lens tolerance. Consultation with your opthalmologist can help with this. 

Rare but serious side effects:

• Blood clots

  • BCPs can make users slightly more prone to form blood clots. A blood clot can occur in a vein or artery and can have different symptoms depending on where it forms. Clots can occur in the legs, abdomen, heart, lungs, eye, or brain. In the brain, a clot could manifest as a stroke. The risk of these events occurring is very low, but increases in people over 35, in smokers, and in those with high blood pressure, heart disease, diabetes, clotting tendency, or a family history of clotting abnormalities. The warning signs of a blood clot spell out the word ACHES:

    • Abdominal pain

    • Chest pain (also shortness of breath)

    • Headaches (especially those that are new, severe, or associated with persistent dizziness, difficulty speaking, fainting,numbness or weakness in extremities

    • Eye problems (blurred vision or loss of vision)

    • Severe leg pain (and/or redness and swelling in the calf or thigh)

  • If you develop any of the ACHES side effects or jaundice (a yellowing of the eyes or skin) while on birth control pills, call Health Services right away at 401.863-1330. If you need emergency medical attention, call EMS at 401.863-4111. If you are out of town, contact a local health provider or go to a hospital emergency room.

• High blood pressure

  • Birth control pills can raise your blood pressure. This is why your medical provider will check your blood pressure a few months after you begin taking the birth control pills.

• Liver tumors

  • Birth control pills have been associated with an increased risk of forming benign liver tumors. This is a very rare occurrence, but you should contact your provider if you develop upper abdominal pain while taking birth control pills. Additionally, birth control pills may accelerate the formation of gallbladder stones in users who have a strong family history of gallstone disease.

• Breast cancer risk

  • Many patients ask about how birth control pills affect their future risk of developing breast cancer. Most of the literature suggests that use of the birth control pill has little if any effect on the risk of breast cancer. One more recent study did show an elevated risk of breast cancer among long term users of the pill, but the increase in risk was still small.

• Cervical cancer risk

  • The risk of developing this type of cancer is slightly increased in birth control pills users. Fortunately, routine Pap smear testing is an excellent screening tool. 

A one month supply of birth control pills, if you are paying out of pocket, averages between $15 and $30, at the Health Services pharmacy. If you use your insurance, co-pays will vary by carrier but for many you will be able to find a pill with a no co-pay option. If you have Brown's student health insurance, there is no co-pay for contraceptives. 

Missing pills or starting the pack late may make your pill less effective. The chance of pregnancy after missing pills depends on when pills are missed and how many pills are missed. A pill is late when you have forgotten to take it at the usual time. A pill has been missed when it is more than 24 hours since the time you should have taken it.

If you miss 1 pill anywhere in your pack, or start the new pack 1 day late, you will still have contraceptive coverage. However, missing 2 or more pills or starting the pack 2 or more days late (more than 48 hours late) may affect the impact the effectiveness significantly. In particular, during the 7-day pill-free break, your ovaries are not getting any effects from the pill. If you make this pill-free break longer by forgetting 2 or more pills, your ovaries might release an egg and there is a real risk of becoming pregnant.

If you have missed one pill, anywhere in the pack:
• take the last pill you missed now even if it means taking two pills in one day
• continue taking the rest of the pack as usual
• no back-up contraception is needed
• take your placebo pill break as normal

If you have missed two or more pills (more than 48 hours late), anywhere in the pack:
• take the last pill you missed now even if it means taking two pills in one day
• leave any earlier missed pills
• continue taking the rest of the pack as usual and use an extra method of contraception for the next seven days
• you may need to start the next pack of pills without a break. If less than seven active pills are left in the pack after the missed pill, finish the pack and begin new one the next day (this means missing out the break). If seven or more active pills are left in the pack after the last missed pill, finish the pack and have the usual placebo break.
• you may need emergency contraception. If you had intercourse without a condom and have missed two or more pills, Brown students can call Health Services at 401.863-1330 to discuss whether you should consider emergency contraception.

If a pill is lost, you should replace it from a separate pack of pills. Brown students should call Health Services at 401.863-1330 if this happens. Advice may vary depending on where you are in your pack and what type of pill you are on.

There may be a week when you would really like to avoid your period because of a special trip or event. You may accomplish this by not taking the placebo week of pills. Instead, throw them out and start your next pack of pills. Your period should hold off until you finish this new pack. This works a bit better with monophasic pills than with triphasic pills. If you'd like to try this method, call your provider to discuss the details.

Spotting or bleeding during the active pills of your pack is termed breakthrough bleeding. It is very common during the first three months of pill use. This bleeding can usually be ignored and should resolve by the third pack. If light bleeding persists for more than 5 to 7 days or heavy bleeding persists for more than 2 to 3 days, call your provider. They will sometimes recommend taking two pills a day (one it the morning, one in the evening) until the bleeding stops. The extra pills should be drawn from a separate pack of pills. Usually the extra pills need to be taken for 2 to 3 days. Breakthrough bleeding can also occur if you are late or forgot a pill. If you are experiencing breakthrough bleeding after your 3rd month of pill use for no obvious reason (you've taken your pills perfectly), you should call your provider.

There is no evidence that birth control pill usage at any time is related to infertility.