Combination birth control pills contain both estrogen and progesterone. The hormones prevent pregnancy by stopping ovulation and changing the lining of your uterus (womb) and your vaginal discharge to prevent sperm from entering your body.

Some people have side effects when taking birth control pills with estrogen. Low-dose pills contain less estrogen than high-dose pills, which may help reduce unwanted side effects.

There isn’t one birth control pill that’s right for everyone. If you’re experiencing side effects from your birth control, your healthcare provider can discuss potential changes to your type or dosage of birth control.

Combination birth control pills contain both progesterone and estrogen. While the amount of progesterone in these pills stays the same, the amount of estrogen can vary. The type of estrogen in combination pills is usually ethinyl estradiol.

High Dose

High-dose combination birth control pills contain 50 micrograms of estrogen or less. These are prescribed less frequently than birth control pills with lower doses of estrogen as they are more likely to produce negative side effects.

Low Dose

Low-dose combination birth control pills usually contain 20-35 micrograms of estrogen. Pills with 20-25 micrograms of estrogen are best for people who experience negative side effects at doses of 30-35 micrograms of estrogen.

For example, 20-microgram doses may be less likely to cause irregular bleeding for some individuals.

Ultra Low Dose

Ultra-low-dose birth control pills have between 10-20 micrograms of estrogen. These are best for people who are very sensitive to negative side effects when taking combination birth control pills.

You might think that a lower dose birth control pill may not work as well to prevent pregnancy. However, research has found that both high- and low-dose birth control pills work just as well to prevent pregnancy.

One review of 13 studies found that birth control pills containing 20 micrograms of estrogen were just as effective at preventing pregnancy as birth control pills containing less than 20 micrograms.

All birth control pill types have similar effectiveness rates for preventing pregnancy. When you use birth control pills perfectly (taking the pills exactly as instructed by your healthcare provider), you have a 0.3% chance of getting pregnant in one year of use. If you use birth control less consistently, you will have about a 9% chance of getting pregnant in one year of use.

Whatever dose of birth control pill you use, it’s important to use the pills according to the instructions your healthcare provider gave you.

Correct birth control use can look different depending on the type. For example:

• Monthly dosing: Some birth control pills require you to take an “active pill” containing estrogen and progestin for 21-24 days and then take a placebo pill (no hormones) or no pills for 4-7 days.
• Three-month dosing: Other types require you to take the same pill for longer periods, such as 84 days in a row, followed by a placebo pill for seven days.
• Year-long dosing: Some types require you to take an active pill every day for a year.

There are two main types of birth control pills prescribed by doctors and healthcare providers:

• Combination pills, which contain estrogen and progesterone
• Progestin-only pills (mini pills)

All combination pills contain progesterone and estrogen, though the type of progestin may vary. The type of estrogen is the same across all pills, but the amount can differ. Combination pills may contain anywhere from 10-50 micrograms of estrogen.

Progestin-only pills only contain the hormone progesterone. In this way, they are a “low dose” pill because they contain zero estrogen. These are good choices for people who cannot take estrogen for medical reasons or are concerned about the side effects and risks of taking estrogen.

There are currently only two progestin-only pills available for birth control, and they contain different progestins.

The first available combination birth control pills contained 50 micrograms of estrogen. However, these pills were soon linked to blood clots in veins. This health risk is partly why lower-estrogen combination birth control pills became available and are now recommended for most people.

Beyond more serious risks like blood clots, birth control pills can have uncomfortable side effects for some people, and taking a lower-dose pill may reduce some of these side effects, such as:

Symptoms of decreased sex drive do not usually improve after taking a lower dose of birth control pills. If you experience severe period pain, an extended-release birth control pill may be better. If breakthrough bleeding is excessive, switching to a higher dose of estrogen may reduce this symptom.

There is no exact dose that will lower these effects, as it’s particular to the individual. People usually work with their healthcare provider to find a dose that produces the fewest side effects.

High- and low-dose birth control pills have similar benefits and disadvantages. Taking a lower-dose combination pill may reduce side effects like headaches, nausea, and breast soreness.

The overall benefits of combination birth control pills include:

• Shorter periods or lack of periods
• Reduced premenstrual syndrome (PMS) symptoms
• Reduced risk of ovarian cancer, uterine cancer, and colon cancer
• Treatment of polycystic ovarian syndrome (PCOS)
• Fewer ovarian cysts and ovarian tumors
• Lower risk of anemia (low iron)

Some possible disadvantages of combined birth control pills include:

• Side effects like breast soreness, nausea, and headaches
• Irregular bleeding and breakthrough bleeding
• Potential increase in blood pressure
• Increased risk of deep venous thrombosis (a blood clot forming in a vein), especially with higher estrogen doses

While most people can safely take combination birth control pills, some populations should avoid them. This includes people who:

• Have given birth within the past 21 days
• Have a history or elevated risk of blood clots in their veins
• Have a current cancer diagnosis
• Have a current breast cancer diagnosis
• Are recovering from major surgery and are currently immobile (unable to get around easily)
• Have a history of migraines with aura (vision changes and other sensory changes)
• Are over the age of 35 and smoke
• Have high blood pressure (even when managed with medication)
• Have a history of heart disease or stroke
• Have a history of diabetes (with certain complications)

Combination birth control pills contain both estrogen and progesterone. Birth control pills containing estrogen may cause unpleasant side effects, like nausea, headaches, and sore breasts.

Taking a birth control pill with a lower dose of estrogen may help reduce these side effects. Higher doses of estrogen may also increase your risk for blood clots.

Talk to your healthcare provider about which birth control type is best for you, and follow their instructions for taking birth control to maximize effectiveness.