Heavy Periods: The Blood Tests Every Woman Should Know About

Why Heavy Periods Might Be More Than You Think

You go through pads or tampons faster than feels normal. You might pass clots. Your period lasts longer than a week. And the fatigue that comes with it makes everything harder. But because heavy periods are so common, many women assume this is just how it is.

Heavy menstrual bleeding (menorrhagia) affects about 1 in 5 women. While it can be caused by structural issues like fibroids or polyps, hormonal and nutritional factors play a huge role. Blood tests can identify these causes and guide treatment that goes beyond just managing symptoms.

What Your Body Might Be Telling You

Iron deficiency is both a cause and a consequence of heavy periods. Heavy bleeding depletes your iron stores, which makes you tired and weak. But low iron can also make bleeding heavier by affecting platelet function and blood vessel integrity. It becomes a vicious cycle.

Thyroid dysfunction affects your menstrual cycle directly. An underactive thyroid (hypothyroidism) can cause heavier, longer periods. An overactive thyroid can make them lighter or irregular. Either way, thyroid function should be checked.

Hormonal imbalances, particularly low progesterone relative to estrogen (estrogen dominance), are a common cause of heavy periods. Progesterone stabilizes the uterine lining. Without enough of it, the lining builds up excessively and sheds heavily.

Coagulation disorders like von Willebrand disease are more common than most people realize and can cause heavy periods from puberty onward.

The Blood Tests That Can Help

• CBC (Complete Blood Count), Shows whether heavy bleeding has caused anemia.
• Serum Ferritin, Reveals iron stores. This is critical because ferritin drops before hemoglobin does.
• Iron Studies (Serum Iron, TIBC, Transferrin Saturation), Complete picture of iron metabolism.
• Thyroid Panel (TSH, Free T4), Rules out thyroid dysfunction as a cause.
• Progesterone (Day 21), Checks whether you are ovulating and producing adequate progesterone.
• Estradiol, Helps assess the estrogen-progesterone balance.
• PT, PTT, and Platelet Count, Screens for bleeding disorders.
• Von Willebrand Factor, If a bleeding disorder is suspected based on history.

The Key Insight Your GP Might Miss

Heavy periods deplete iron, and low iron makes periods heavier. This cycle can go unrecognized for years. If you have heavy periods, checking ferritin is essential, not just hemoglobin. A ferritin below 30 in the context of heavy periods needs treatment.

Take Control of Your Health

Heavy periods are not something you just have to live with. Understanding the underlying cause through blood testing opens the door to treatment that addresses the root problem.

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