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Birth Control Injection Side Effect: What Should I be Prepared for?

Medically reviewed by John Paul Abrina, MD · Oncology · Davao Doctors Hospital

Written by Gerard Tamayo · Updated Jul 13, 2022

Birth Control Injection Side Effect: What Should I be Prepared for?

The injectable birth control medroxyprogesterone acetate is a form of birth control that you can inject into your upper arm or buttocks. This type of shot should be taken every three months to maximize its effectiveness and consistency. Once you take the shot, you should be safe to have sex for 13 weeks with a relatively low likelihood of becoming pregnant. What are some birth control injection side effects?

How Does it Work?

The “depo shot”, or any other injectable contraceptives containing medroxyprogesterone acetate (a progestin) helps prevent you from becoming pregnant. 

The injectable works by suppressing ovulation, making your ovaries unable to release a mature egg for fertilization. It also thickens the mucus of your cervix, which makes it difficult for sperm to pass through. By preventing the meeting of the mature egg of a woman and the sperm of a man, it makes the process of getting pregnant very difficult.

Who Can’t Take Injectable Contraceptives?

The following should avoid this means of contraceptive:

  • Breastfeeding women who have delivered their baby less than six weeks prior to the injection
  • People who are at risk for cardiovascular disease (old age, smokers, diabetics, hypertensives)
  • Those who suffer from Deep Vein Thrombosis
  • People currently with or have a history of cardiovascular disease or stroke
  • People who have had a history of breast cancer with no evidence of the disease within the last five years
  • Those with unexplained vaginal bleeding
  • People with systemic lupus erythematosus (SLE)
  • People with complicated diabetes
  • Those with liver cirrhosis and/or liver tumors
  • People who have breast cancer MUST NOT take injectable contraceptives.

    What Do I Do When I Go in for My Shot?

    When availing of an injectable contraceptive, you will be given one shot. You’ll have to come back for another every 12-13 weeks or 3 months, making a total of 4 shots a year. You don’t have to do anything prior to receiving your first shot, and if you have your first shot at 7 days after the start of your period, the effects of the shot will immediately protect you from pregnancy. However, if your shot was administered at any other time during your cycle, you’ll have to use other forms of contraceptives for at least a week before the drug takes effect.

    After taking your first shot, be sure to take note of when your next check up and shot administration will be (3 months from your first shot) by marking it on a calendar or having your partner remind you.

    What Happens if I Miss One of My Shots?

    If you miss your follow-up shot and have sex within 2 weeks after your scheduled shot, you may have to take a pregnancy test as the effect of the progesterone shot may have already worn off, exposing you to becoming pregnant.

    What are the Birth Control Injection Side Effects?

    The most commonly seen birth control injection side effects of medroxyprogesterone acetate (MPA) are weight gain and menstrual irregularities.

    Studies have shown that people typically gain an average of around 3 kilograms while taking MPA. Half of the people who take MPA have noted having irregularity in their menses during their first year of taking the drug.

    After around 2 years, the menstrual irregularities occur less frequently and decrease the longer you take the contraceptives. In fact, some studies show that half the people actually experience amenorrhea (absence of menstruation) during their first year of taking the drug. 

    The most relevant birth control injection side effects of injectable include delayed return to fertility, unexpected pregnancy, uterine hyperplasia, and hemorrhage (when your uterus thickens), genitourinary infections, and vaginal cysts.

    Advantages of Injectable Progestin Contraceptives

    Injectable contraceptives are good for long-term protection from pregnancy and are reversible. The following are other advantages:

    • It doesn’t require daily intake 
    • It doesn’t interfere with sex 
    • Has no side effects related to estrogen, as these are purely progesterone
    • Does not affect the amount and quality of the breast milk you produce

    Disadvantages of Injectable Progestin Contraceptives

    • Delayed return to fertility
    • You will have to take another shot every 2-3 months (You may forget to follow up)
    • Has no protection from STDs
    • Can cause menstrual irregularity during the first few months or first year of use, and even amenorrhea
    • Possible bone density loss for long term users

    Am I Safe From Sexually Transmitted Infections?

    As the shot only helps in preventing pregnancy, it does not physically form a barrier that could protect you from STIs, since these are usually spread via direct sexual contact. If you want to prevent STIs, it is recommended that you use barrier contraceptives.

    What Brands are Available in the Philippines?

    In the Philippines, DMPA (Depo-Provera), DMPA (Depo-Trust) and NET-EN (Noristerat) are the only available progestin injectables. 

    Key Takeaways

    Injectable Contraceptives are a relatively safe form of contraception. These injections can protect you from pregnancy for at least 3 months, at which point you will have to undergo a follow up shot. Consult your doctor regarding this form of contraception. 

    Learn more about Contraception here. 


    Hello Health Group does not provide medical advice, diagnosis or treatment.

    Medically reviewed by

    John Paul Abrina, MD

    Oncology · Davao Doctors Hospital

    Written by Gerard Tamayo · Updated Jul 13, 2022

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