Oral Contraceptives Cause A Five-Fold Increase In The Risk Of Blood Clots

Blood clots are one of the most common side effects of oral contraceptives. According to a study published in the August 14, 2009 issue of the British Medical Journal, women taking currently available oral contraceptives have approximately a five-times increased risk of developing venous thrombosis (blood clots) compared to non-users. Also, two physicians published a Clinical Opinion in the January 2013 issue of the Journal of Obstetrics and Gynecology that discussed the increased cardiovascular risks from oral contraceptives.    

The increased risk of blood clots is true of women who take oral contraceptives AND for women who take oral estrogen medications to treat the symptoms of menopause. One of the main mechanisms responsible for the development of blood clots is low levels of the mineral magnesium.

Oral ingestion of estrogen-containing medications decreases magnesium levels, which substantially increases the risk for blood clots. I want to explain why this happens and tell women who take oral estrogen medications (birth control pills and menopausal hormone replacement therapy/HRT medications) what they can do to reduce the risks of developing blood clots.

One of the mechanisms that regulate the blood clotting process is the balance between calcium and magnesium. Calcium is a cofactor for the production of fibrin, which is a protein that stimulates the formation of blood clots. On the other hand, magnesium helps thin the blood and acts to dissolve blood clots. Hence, the delicate balancing act between the ratio of calcium and magnesium in the blood is one of the key methods the body uses to control and regulate the blood clotting mechanism.

For many women, taking oral estrogen medications is a double whammy for increased risks of blood clots. Frequently women are advised to take calcium to help prevent osteoporosis. At the same time, estrogen-containing medications deplete magnesium. Both of these effects create a wider gap between the normal balance between calcium and magnesium. Elevated calcium and/or a deficiency of magnesium, increases the risk of forming blood clots. I first learned about this risk in an article published in the journal Magnesium Research which was titled Increased Need For Magnesium With The Use of Combined Oestrogen And Calcium For Osteoporosis Treatment (note the British spelling for estrogen).

I recommend that women take 500 mg of magnesium twice daily to improves the calcium/magnesium balance and reduce the risk of blood clots.  I also strongly recommend that women (and men and children) take omega-3 fish oil supplements on a daily basis. Omega-3 fish oils act as mild blood thinners which will also reduce the risk of blood clots. 

All of the side effects of oral contraceptives are discussed and explained in my new book The Pill Problem.

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