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The oral contraceptive pill, commonly known as “the pill,” is a hormone-based method of preventing pregnancy. It can also help resolve irregular menstruation, painful or heavy periods, endometriosis, acne, and premenstrual syndrome (PMS).

Birth control pills work by preventing ovulation. No egg is produced, so there is nothing for the sperm to fertilize. Pregnancy cannot occur.

“The pill” is used by nearly 16 percent of women aged 15 to 44 years in the United States, and it has both advantages and disadvantages. People with different risk factors may be advised to use a particular kind of pill.

There are different types of contraceptive pills. They all contain synthetic forms of the hormones estrogen, progesterone, or both. Synthetic progesterone is called progestin. Combination pills contain progestin and estrogen. The “mini pill,” contains only progestin.

Monophasic pills all contain the same balance of hormones. With phasic pills, two or three different types of pill are taken each month, each with a different balance of hormones.

Another option is “everyday pills” and “21-day pills.” A pack of everyday pills lasts 28 days, but seven of the pills are inactive. The everyday pill may be easier to use correctly, as the routine is the same every day.

Used correctly, the pill is highly effective, but because people make mistakes, 6 to 12 pregnancies in every 100 are thought to occur each year while using it. The Centers for Disease Control and Prevention (CDC) put the failure rate for both types of pill at 9 percent.

Birth control pills do not prevent sexually transmitted diseases (STDs). Only a condom can help prevent this type of infection.

Common side effects of oral contraceptives include:

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Hormonal contraception is taken to prevent pregnancy and for other medical reasons.
  • intermenstrual spotting
  • nausea
  • breast tenderness
  • headaches and migraine
  • weight gain
  • mood changes
  • missed periods
  • decreased libido
  • vaginal discharge
  • changes to eyesight for those using contact lenses

We will look at each of these side effects in detail below.

1. Intermenstrual spotting

Breakthrough vaginal bleeding is common between expected periods. This usually resolves within 3 months of starting to take the pill.

During spotting, the pill is still effective, as long as it has been taken correctly and no doses are missed. Anyone who experiences 5 or more days of bleeding while on active pills, or heavy bleeding for 3 or more days, should contact a health care professional for advice.

This bleeding may happen because the uterus is adjusting to having a thinner endometrial lining or because the body is adjusting to having different levels of hormones.

2. Nausea

Some people experience mild nausea when first taking the pill, but symptoms usually subside after a while. Taking the pill with food or at bedtime may help. If nausea is severe or persists for longer than 3 months, you should seek medical guidance.

3. Breast tenderness

Birth control pills may cause breast enlargement or tenderness. This normally resolves a few weeks after starting the pill. Anyone who finds a lump in the breast or who has persistent pain or tenderness or severe breast pain should seek medical help.

Tips for relieving breast tenderness include reducing caffeine and salt intake and wearing a supportive bra.

4. Headaches and migraine

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Some people experience side effects with “the pill,” such as irregular periods, nausea, headaches or weight change.

The hormones in birth control pills can increase the chance of headaches and migraine.

Pills with different types and doses of hormone may trigger different symptoms.

Using a low-dose pill may reduce the incidence of headaches.

Symptoms normally improve over time, but if severe headaches start when you begin taking the pill, you should seek medical advice.

5. Weight gain

Clinical studies have not found a consistent link between the use of birth control pills and weight fluctuations. However, fluid retention may occur, especially around the breasts and hips.

According to one review, most studies have found an average weight gain of under 4.4 pounds (2 kilograms) at 6 or 12 months with progestin-only birth control. Studies of other birth control methods showed the same gain.

Some types of hormonal contraceptive have been linked to a decrease in lean body mass.

6. Mood changes

Studies suggest that oral contraceptives may affect the user’s mood and increase the risk of depression or other emotional changes. Anyone experiencing mood changes during pill use should contact their medical provider.

7. Missed periods

Even with proper pill use, a period may sometimes be missed. Factors that can influence this include stress, illness, travel, and hormonal or thyroid abnormalities.

If a period is missed or is very light while using the pill, a pregnancy test is recommended before starting the next pack. It is not unusual for a flow to be very light or missed altogether on occasion. If concerned, seek medical advice.

8. Decreased libido

The hormone or hormones in the contraceptive pill can affect sex drive or libido in some people. If decreased libido persists and is bothersome, this should be discussed with a medical provider.

In some cases, the birth control pill can increase libido, for example, by removing concerns about pregnancy and reducing the painful symptoms of menstrual cramping, premenstrual syndrome, endometriosis, and uterine fibroids.

9. Vaginal discharge

Changes in vaginal discharge may occur when taking the pill. This may be an increase or a decrease in vaginal lubrication or a change in the nature of the discharge. If vaginal dryness results, added lubrication can help make sex more comfortable.

These changes are not usually harmful, but alternations in color or odor could indicate an infection. Anyone who is concerned about such changes should speak with their medical provider.

10. Eye changes

Hormonal changes caused by the birth control pill have been linked to a thickening of the cornea in the eyes. Oral contraceptive use has not been associated with a higher risk of eye disease, but it may mean that contact lenses no longer fit comfortably.

Contact lens wearers should consult their ophthalmologist if they experience any changes in vision or lens tolerance during pill use.

The combined pill can increase the risk of cardiovascular problems, such as blood clots, deep vein thrombosis (DVT), a clot on the lung, a stroke or heart attack.

Birth control pills have also been associated with an increase in blood pressure, benign liver tumors, and some types of cancer.

The pill should not be taken by:

  • women who are pregnant
  • smokers over the age of 35 years, or anyone who stopped smoking within the last year and is over 35 years old
  • anyone with obesity
  • those who are taking certain medications
  • anyone who has or has had thrombosis, a stroke, or a heart problem
  • anyone with a close relative who had a blood clot before the age of 45 years
  • people who have severe migraines, especially with an aura as the warning sign
  • anyone who has or had had breast cancer or disease of the liver or gallbladder
  • anyone who has had diabetes for at least 20 years or diabetes with complications

If any of the following occur, the user should see a doctor.

  • abdominal or stomach pain
  • chest pain, shortness of breath, or both
  • severe headaches
  • eye problems such as blurred vision or loss of vision
  • swelling or aching in the legs and thighs
  • redness, swelling or pain in the calf or thighs

They may indicate a more serious condition.

Use of birth-control pills may increase the risk of long-term health problems.

Cardiovascular problems

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People with a history of blood clots, heart attacks or stroke are advised not to take the combination birth control pill.

Combination pills can slightly increase the risk of cardiovascular side effects, such as heart attack, stroke, and blood clots. These can all be fatal.

The risk is higher with some pills. A doctor can advise on suitable options.

Anyone who has uncontrolled high blood pressure or a personal or family history of blood clots, heart attack, or stroke should ask their medical provider about alternative methods.

Cancer risk

Female hormones that occur naturally, such as estrogen, are thought to affect the chances of a woman developing some types of cancer. It is therefore possible that using a hormone-based method of birth control could have a similar effect.

Ovarian and endometrial cancer: These appear to be less likely among women who use the pill.

Breast cancer: There appears to be a slightly higher chance of breast cancer developing in women who have recently been using the contraceptive pill, and especially if they started using it during their teenage years. However, after 10 years of not using the pill, the risk appears to be the same as for someone who has never used it.

Other factors may play a role, such as a woman’s age at starting puberty and menopause, her age at her first pregnancy, and whether or not she has had children.

Cervical cancer: Long-term use of the pill has been linked to a higher risk of cervical cancer, compared with those who have never used it. However, most types of cervical cancer are caused by the human papillomavirus (HPV). Whether HPV is linked to the use of oral birth control pills has not yet been confirmed.

Liver cancer: Oral contraceptives have been linked to a higher chance of developing benign liver tumors, but these rarely become cancerous. Some studies have suggested that liver cancer risk is higher after using oral contraceptives for at least 5 years, but other studies have not had the same results.

For those who cannot use or do not wish to the birth control pill, other options are available.


This is a barrier method of birth control that prevents sperm from coming into contact with egg cells. Male condoms are sheathes that are placed over the penis. A female condom is a pouch with a ring at each end. It is inserted into the vagina.

Condoms are widely available, but they are often made from latex, which can trigger an allergy in some individuals. Alternative materials include polyurethane or lambskin.

For both types of condom, the risk of it not working is 18 percent or over in a year.


This is a shallow, dome-shaped rimmed cup that is placed in the vagina to block the cervix. Used with spermicide, it prevents the sperm and egg from meeting.

Disadvantages include possible urinary tract infections and vaginal irritation. The irritation may stem from a reaction to the material the diaphragm is made from or the spermicide.

Between 6 and 12 pregnancies occur annually in every 100 women who use it, because of human error.

NuvaRing (vaginal ring)

A plastic ring is inserted into the vagina, and it releases hormones to suppress ovulation. Each month, it is inserted for 3 weeks and removed for 1 week, during which menstruation occurs. These hormones are very similar to the pill, so similar side effects can occur.

Every year, between 6 and 12 pregnancies occur in every 100 women who use it, because of errors in use.

As a hormonal method of birth control, the vaginal ring can have similar side effects to the pill, including intermenstrual spotting, headache, and reduced libido.

Intrauterine devices (IUDs)

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Intrauterine devices offer an alternative to the birth control pill.

A small device made from plastic and copper is inserted into the uterus at the doctor’s office. IUDs can be hormonal or non-hormonal.

Hormonal IUDs thicken the cervical mucus and suppress ovulation. Non-hormonal IUDs produce an inflammatory response in the uterus that is toxic to sperm.

It lasts for up to 10 years and is almost 100 percent effective at preventing pregnancy.

Adverse effects include intermenstrual spotting and irregular menses. Some IUDs can lead to heavier periods with worsened cramps.

Contraceptive implants

A small, plastic rod is implanted into the upper arm during minor surgery. For the next 3 years, it releases a hormone to thicken cervical mucus, thin the endometrial lining and suppress ovulation. It is almost 100 percent effective.

Side effects are similar to those of the birth control pill. They include abdominal, back pain, and a higher risk of noncancerous ovarian cysts. Many women report diminished or missed periods after several months of use.


Surgery is carried out in the man, to block or cut the tubes that transport sperm from the testicles to the penis. In the woman, surgery blocks the fallopian tubes.

Possible complications for men include infection, hematoma, bruising, and the formation of sperm granulomas, lumps developing in the tissue surrounding the vas deferens where sperm have leaked out.

This is normally permanent.

Having a shot of contraceptive hormones can be a more reliable way of preventing pregnancy than using a pill, as the user does not have to remember to take it at the same time every day.

However, being hormonal methods of birth control, these can also have adverse effects.

Injections such as Depo-Provera suppress ovulation and thicken cervical mucus to reduce the chances of sperm from reaching egg cells, just as the birth control pill does. It is a progestin-only contraceptive (POC).

The advantage of the shot is that you do not have to take it every day, but you do have to remember to have another shot every 3 months, and this must be done at the doctor’s office.

It is more than 99 percent effective when used correctly. However because women sometimes forget to have another shot, around 6 out of every 100 women will become pregnant each year when using it. This makes it more reliable than oral contraception.

Some of the shot’s side effects are similar to those of the birth control pill.

Anyone who has had breast cancer is advised to not to use it. It may also increase the risk of Chlamydia and HIV, but why this should be remains unclear.

Oral contraceptives have been associated with cardiovascular problems. Some studies have linked the shot with thrombosis, or blood clotting, but others have not.

The Mayo Clinic notes that some providers may discourage its use in people with a history of heart disease, diabetes, or stroke.

Possible adverse effects that should be reported to a doctor include:

  • depression
  • migraine
  • vaginal bleeding that is heavier or lasts longer than usual
  • jaundice, or yellowing of the skin and eyes
  • pus and pain around the injection site

Other effects that tend to pass within a few months include:

  • abdominal pain and bloating
  • decrease libido
  • dizziness
  • nervousness
  • weakness and fatigue
  • weight gain

Depo-Provera has also been linked to a loss of bone mineral density, increasing the risk for osteoporosis and bone fracture in later life.

Even when used correctly, pregnancy can occur with the shot. After stopping it, it can take up to 10 months to conceive.

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