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Types of Birth Control Pills

Phases

Originally, birth control pills contained only one phase (these are known as monophasic birth control pills). This means that the strength of hormones does not vary throughout the cycle, expect for the inactive pills with no active hormones in the end of the pack.
Many birth control pills used today are monophasic. Some contain two different phases of hormones; these are known as biphasic birth control pills. Triphasic birth control pills, which contain three different phases of hormones, have recently become popular. Even four-phasic birth control pills (which, as the name implies, have four phases of hormones) are now available.
Biphasic, triphasic, and four-phasic birth control pills are thought to more closely match the hormonal changes that occur in a woman's cycle, compared to monophasic pills. Biphasic, triphasic, and four-phasic pills may also allow for a lower total exposure to hormones, compared to monophasic pills.

Other Categorizations

Some birth control pills are classified as either extended-cycle pills, which decrease the number of menstrual periods per year, or continuous-cycle pills, which completely eliminate scheduled menstrual periods. Both extended-cycle and continuous-cycle birth control pills offer the convenience of fewer menstrual periods, although breakthrough bleeding (bleeding between periods) may be more common.
Some birth control pills have iron added to the inactive pills at the end of each pack. Most of these pills have the word "Fe" in the name, since this is the chemical symbol for iron. Such pills may decrease the risk of anemia due to blood loss from menstruation.
Some birth control pills have a shortened inactive pill phase, such as four days instead of seven.
Last reviewed by: Kristi Monson, PharmD
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