How you prepare

You'll need to request a prescription for combination birth control pills from your health care provider. Your health care provider will check your blood pressure, check your weight and review your medical history, including medications you're taking.

He or she will also ask about your concerns and preferences to help determine which combination birth control pill is right for you. Health care providers generally recommend pills with the lowest dose of hormones that will help prevent pregnancy, give you important noncontraceptive benefits and minimize side effects.

Although the amount of estrogen in combination pills can be as low as 10 micrograms (mcg) of ethinyl estradiol, most pills contain about 35 mcg. Low-dose pills can result in more breakthrough bleeding than pills with more estrogen.

Combination pills are categorized based on whether the dose of hormones stays the same or varies:

• Monophasic. Each active pill contains the same amount of estrogen and progestin.
• Biphasic. Active pills contain two combinations of estrogen and progestin.
• Triphasic. Active pills contain three combinations of estrogen and progestin. In some types, the progestin content increases; in others the progestin dose remains steady, and the estrogen content increases.