What it is

Known as “The Shot,” Depo-Provera® is a brand name for a contraceptive injection that contains the hormone progestin. Its contraceptive effects last a minimum of three months. Depo-Provera is one of the most commonly used contraceptives, chosen by an estimated 74 million women worldwide.

While it might seem that a form of birth control used by so many women couldn’t possibly be that bad, the Depo shot also appears to be one of the most dangerous of all hormonal birth control options. And, once the long-lasting shot is injected into a woman’s body, she has no option for reversing its adverse effects other than waiting for it to wear off.

How it works

The Depo shot contains medroxyprogesterone acetate (MPA), a commonly used synthetic progestin. MPA is a chemical that approximates a woman’s natural hormones to prevent ovulation (release of an egg from the ovary) by suppressing the normal brain signals that govern a woman’s menstrual cycle. The shot acts further to thicken cervical mucus to block sperm from entering the uterus and fertilizing the egg. Lastly, it thins the uterine lining so that in case pregnancy does occur, the embryo will find an inhospitable environment when it attempts to implant in the uterus. The combined effects of the Depo shot mean that it is over 99 percent effective at preventing pregnancy when injections are received every 10-15 weeks.

Serious risks

Starting in 2004, the FDA required Depo to carry on its package insert a “black box warning”—the agency’s highest level of alert on pharmaceuticals. The boxed warning is intended to underscore serious and potentially life-threatening adverse drug reactions. In the case of Depo, the notice cautions users about the danger of bone density loss due to lowered estrogen levels in the body, which is caused by the shot.

The boxed warning advises that “women who use Depo-Provera Contraceptive Injection may lose significant bone mineral density. Bone loss is greater with increasing duration of use and may not be completely reversible.” Bone density loss can lead to bone fractures and early onset of osteoporosis.

The Depo shot also suppresses the immune system by increasing cortisol levels in the body. As a result, its use can lead to increased susceptibility to sexually transmitted diseases, notably HIV, from men to women. In observational studies, Depo-Provera has been associated with two to four times the normal risk of contracting HIV.

The Depo shot has also been associated with pseudotumor cerebri (false brain tumor), which is a serious neurological condition. This is a rare but serious effect that results in debilitating symptoms that mimic those of a brain tumor: severe headaches, and hearing and vision problems, including blindness.

Other Side Effects

Over five percent of women studied reported the following side effects while on Depo Provera: headache, abdominal pain, weight gain, nervousness, dizziness, loss of libido. Other common side effects include fatigue, irritability, acne, and hair loss.

With the shot, a “woman’s own hormone levels become almost as low as in menopause, with very low progesterone and lowered estrogen levels,” explains Laura Werschler, former editor-in-chief of Women’s Reproductive Health, the journal of the Society for Menstrual Cycle Research.

This reduction of natural hormone levels prevents the menstrual cycle from progressing normally, and so prevents pregnancy from occurring. In fact, the number one side effect of the shot is menstrual irregularities. Typically, women experience bleeding between periods, an increase or decrease in bleeding during the period, and often no period at all. About half of women on Depo Provera cease to have periods after the first year of use.

While many women may welcome the loss of a period, it is a side effect that causes its own set of adverse effects. The return to normal menstruation and fertility can take up to 18 months after use of Depo.

Lasting effects

Not only can side effects continue well after the last shot wears off, but furthermore, signs of a Depo-withdrawal or discontinuation syndrome have been observed, i.e., some women report difficulties that begin only after the shot is discontinued. While we currently lack formal medical studies on this phenomenon, in 2018, the government of New Zealand worked with a Medicines Adverse Reactions Committee (MARC) who studied the question largely through women’s reports of problems on social media. Their report provides a thorough look at Depo and its range of adverse affects, including the effects of its discontinuation.

Dr. Jerilynn C. Prior, one of the MARC members, is a Society for Menstrual Cycle Research board member, professor of endocrinology at the University of British Columbia, and scientific director of the Centre for Menstrual Cycle and Ovulation Research. Dr. Prior postulates that because Depo suppresses a woman’s reproductive system, the brain and reproductive system “have ‘forgotten how’ to coordinate their usual complex and amazing feedback needed for normal ovulatory menstrual cycles.”

She goes on to explain that because “our bodies are programmed to work hard to regain reproduction,” the hormones fall out of balance when a woman begins overproducing estrogen before ovulation is restored. Healthy ovulation triggers the production of progesterone, which would normally counterbalance high levels of estrogen.

In the same way, the body appears to work extra hard once Depo is out of its system to make up for bone loss density caused by the drug. Use of Depo is one factor of several that can contribute to abnormally low bone density. For this reason, women are advised to limit use of Depo to two years.

Public action against Depo Provera

A number of lawsuits have already been brought against Pfizer for complications linked to the injectable contraceptive, including a $700 million class action lawsuit filed in Canada, alleging bone loss and osteoporosis side effects. In 2010, Pfizer settled several class action lawsuits involving problems with the drug, and product liability lawyers around the country are now investigating claims by women who received Depo-Provera injections in the past and have since suffered serious medical conditions.

A Citizen’s Petition to the FDA from the Contraceptive Study Group is currently requesting greater transparency on the dangers of various pharmaceutical birth control methods and asks the FDA specifically to remove the Depo shot from the market based on evidence that it facilitates the transmission of HIV from men to women. The petition is founded upon a comprehensive literature survey by a group of experts, in which evidence shows these products to lead to 14 major health conditions from cancer and blood clots to auto-immune disease.

If you have experienced side effects or health complications on the Birth Control Shot, share your story.

Natural Alternatives to Birth Control

Safe, side effect-free, and effective natural birth control options based on learning the signs that mark the fertile and infertile phases of a woman’s cycle, are known as fertility awareness or natural family planning methods. These methods also serve as practical tools for monitoring reproductive health while offering the many health benefits of a naturally functional fertility cycle.

Depo Provera® is a registered trademark of Pfizer.