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Can Birth Control Pills Weaken Your Bones?

Oral contraceptives, or birth control pills, are taken by countless women in an effort to avoid unwanted pregnancy. Bone mineral density (BMD) is a measure of how strong bones are - and how likely they are to break.

Studies have shown an association between these pills and changes in BMD and fracture rates. Although most data regarding oral contraceptives suggest that they increase BMD, few of these studies have focused on premenopausal women who use “the pill” for birth control.

A study in the Canadian Medical Association Journal focused on the bone densities of young women using birth control. Over 500 women ages 25 to 45 were evaluated for oral contraceptive use, lifestyle trends, sociodemographics, and medical histories in the Canadian Multicentre Osteoporosis Study. Only women who had used birth control pills for at least three months were considered users. BMD was measured in the spine, upper leg, and pelvis using a type of x-ray.

BMD values were lower at all measurement sites in women who used oral contraceptives, compared to women who had never used them. BMD was reduced 2- 4%, which may not sound like much. Decreases in BMD this large may translate into an increased fracture risk of 20-30%, however. Eighty-seven percent of the women in this study had used oral contraceptives at some point in their lives for at least three months.

If you or anyone you know is taking birth control, be aware of all possible risks and side effects of the drugs. Talk to your doctor of chiropractic for more information.


Prior JC, Kirkland SA, Joseph L, et al. Oral contraceptive use and bone mineral density in premenopausal women: Cross-sectional, population-based data from the Canadian Multicentre Osteoporosis Study. Canadian Medical Association Journal 2001:165(8), pp. 1023-1029.

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