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Contraception health centre

Contraceptive injections

Contraceptive injections are an alternative to other hormonal contraceptive, such as the Pill. They have the advantage of lasting for some weeks rather than having to take a daily tablet.

Depo-Provera and Noristerat are the contraceptives injections for women available through the NHS. Depo-Provera is more commonly used.

These contraceptive injections are made up of a hormone similar to progesterone and are given as an injection by a doctor or nurse into a muscle in the woman's arm or buttock.

Each Depo-Provera injection provides protection against pregnancy for up to 12 weeks, and each Noristerat injection is effective for up to eight weeks. The injections must be given on time to stay protected against pregnancy.

How soon do the injections work?

Contraception with Depo-Provera and Noristerat begin immediately after the first injection if given within the first five days of your menstrual period. If given on any other day of the cycle then it only becomes effective after seven days.

How effective are the injections?

Both Noristerat and Depo-Provera are 99% effective in preventing pregnancy. However, they do not prevent the spread of STIs. To help protect yourself from STIs, use a male condom each time you and your partner have sex if either one of you could have an STI.

Can any woman use the injections?

Most women can use Depo-Provera, however, it may not be recommended for women who have:

  • Unexplained vaginal bleeding
  • Liver disease
  • Breast cancer or have had it in the past
  • History of heart disease or stroke
  • Diabetes with complications
  • Risk factors for osteoporosis
  • Diabetes with complications
  • Blood clots

Are there side effects associated with the injections?

Possible side effects include:

  • Irregular menstrual periods, or no periods at all
  • Headaches
  • Nervousness
  • Depression
  • Dizziness
  • Acne
  • Changes in appetite
  • Weight gain
  • Excessive growth of facial and body hair
  • Hair loss
  • Loss of  bone mineral density

Most of the side effects are not common. Change in the menstrual cycle is the most common side effect. You may experience  irregular bleeding or spotting. Since the Noristerat injection is only given once or twice, most side effects will stop after the second injection.

However, with Depo-Provera, after a year of use, about 50% of women will stop getting their periods. Their periods usually return when they discontinue the injections.

Prolonged use of Depo-Provera may result in significant loss of bone mineral density, increasing the  risk of osteoporosis. This risk is more likely for those who have been taking it for longer than two years, particularly when other risk factors for osteoporosis exist, such as family history of osteoporosis and long-term alcohol and/or tobacco use. Although there are no studies to show benefit, it is advised that all women on Depo-Provera get adequate calcium and vitamin D (through diet and/or supplements) to help  prevent osteoporosis.

WebMD Medical Reference

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