How Hormonal Birth Control Causes Anemia

A clue as to why women have higher anemia rates than men

Women who suffer from anemia are sometimes instructed to take hormonal birth control to reverse their anemia or “iron deficiency.”

The logic behind this is that when on “the pill,” a woman no longer has a menstrual bleed. The bleed that a woman may experience when on the pill is a “withdrawal bleed” due to the temporary reduction in supplemental estrogens/progestins. Much less blood is usually lost during the “withdrawal bleed” than during a true menstrual bleed. This is because a true menstrual bleed is triggered by a progesterone withdrawal at the end of the luteal phase which initiates the full shedding of the endometrium. Women on birth control have their progesterone production (and consequential withdrawal) suppressed, and synthetic progestins pay more resemblance to estrogens and androgens than they do progesterone. Thus, women on birth control rarely shed their entire endometrium.

Birth control is meant to reverse anemia by reducing monthly blood, and thus iron, loss. Why then do some women find themselves developing anemia or having their anemia get worse after being put on hormonal birth control?

It’s because anemia is a deficiency of hemoglobin and/or red blood cells, which can have many root causes.

In countries where the food supply is largely iron-fortified, anemias are rarely caused by iron deficiency alone. In some cases, it’s possible to be anemic even if iron stores are excessive.