Many women do not realize that different contraceptive methods use different hormones, and as a result, they make poor decisions when it comes to choosing the right method. There are two primary forms of birth control: progestin-only and combination estrogen-progestin. Both of these methods share many of the same side effects, like weight gain, mood changes, and increased risk of blood clots. Yet, these two methods have some differing side effects that women should strongly review prior to committing to a contraceptive method.

Here are the basic differences between the two types and the risks involved. 


"Progestin" is a synthetic hormone that is modeled after the naturally-occurring hormone called "progesterone." Progesterone levels increase once a month in an effort to make the body more hospitable for a fertilized egg. If the egg is not fertilized, then progesterone levels drop. If the egg is fertilized, then the progesterone levels remain heightened throughout the pregnancy. 

In the early days of birth control, researchers developed contraceptives with progesterone to alter the body's hormone levels. Researchers found that progesterone's half-life, or the amount of time that it remains in the body, is really short; as a result, they developed the synthetic hormone progestin. Progestin mimics progesterone in function, but it has a slightly different molecular structure that gives it a longer half-life.

Progestin-Only Contraceptives

Progestin-only birth control is available in "mini-pills," injections, and implants. To be effective, progestin-only injections must be administered every three months, and implants must be removed and replaced every three years. Mini-pills must be taken at the same time every day. 

Side Effects of Progestin-Only Contraceptives

Mini-pills, injections, and implants all consist of the same synthetic hormone, so the side effects of these contraceptives are all the same as well. The most commonly reported side effects of progestin-only birth control methods include:

  • Loss of bone density with the injection;
  • Irreversible nature of injection and more complicated removal of implant if the patient is unhappy with the method; and
  • Unpredictable bleeding and menstrual cycles.


The other hormone naturally produced in the body is "estrogen." Estrogen hormones, like progesterone, regulate a woman's reproductive system by thickening the uterine walls in preparation for conception, and remaining at high levels to maintain a pregnancy if the egg is fertilized. If no pregnancy occurs, estrogen levels will drop along with progesterone levels. 

Combination Contraceptives

Estrogen is used in contraceptives to keep the uterine walls thin, and as a result, inhospitable for a fertilized egg. Estrogen is commonly paired with progestin in "combination" contraceptive pills. These pills must be taken orally at the same time every day to be effective.

Side Effects of Combination Pills

Like progestin-only birth control methods, combination contraceptives also have potential side effects. Some of the most common serious side effects are:

  • Increased risk of heart attacks;
  • Increased risk of gallbladder disease; 
  • High blood pressure; 
  • Severe headaches and migraines; and
  • Risk of stroke. 

The Bottom Line

One of the largest reasons why women might not want to choose progestin-only injections or implants is because they are so long-lasting. A woman who is not sure how progestin-only hormones will affect her should consider that, once the shot is administered, the medicine cannot be extracted. Similarly, if a woman commits to the expensive implant and does not like it, it becomes a costly mistake.

Yet, women who are older, have high blood pressure, or who smoke should opt for progestin-only methods because of the risks associated with combination pills. On the flip side, women who do not want the irregular menstrual cycles often associated with progestin-only methods, or who have painful periods, can benefit from the estrogen in these combination pills. 

Women should communicate honestly with their ob-gyn doctors about their medical histories. Not all birth control methods are suitable for all women, but by knowing the side effects and the differences, women can make more educated decisions about their contraceptive choices.

For more help or if you have other concerns, contact a professional like Richey Mark E MD PC with any questions you have.