Anaemia from heavy periods: cause and testing

Yes, a heavy period can cause anaemia. If you lose a lot of blood every month, you also lose iron. Over time your iron stores run down and your body makes too little haemoglobin, the protein that carries oxygen.

I see it often: women who have felt tired for months and think it comes with a busy life, while their period is actually the culprit. Blood loss through menstruation is one of the most common causes of iron deficiency in women worldwide. The good news is that a few blood values give you a fairly clear picture of whether this is at play.

Below I explain how heavy blood loss leads to anaemia, which symptoms fit and which values are best to test.

Can heavy menstruation cause anaemia?

Yes. With a heavy period you lose more blood than your body can easily replace, and with that blood you lose iron. You need iron to make haemoglobin. If the stores run empty, iron deficiency develops and eventually anaemia.

According to Thuisarts.nl and the NHG, heavy menstrual blood loss is one of the main causes of anaemia in women of reproductive age. It happens gradually, so you notice the symptoms only late.

You can read more about the broader causes in our overview on anaemia in women.

How much blood do you lose during a heavy period?

With an average period you lose about 30 to 40 millilitres of blood per cycle. Doctors usually speak of heavy blood loss above 80 millilitres per cycle. That is hard to measure, so in practice you mainly look at signals.

Think of bleeding through your protection, having to change a pad or tampon every hour, large clots or a period that lasts longer than seven days. If you recognise this, it is worth having your blood values checked.

What lies behind that heavy blood loss you can read in our article on heavy periods and when to test.

What are the symptoms?

Anaemia from iron deficiency develops slowly, so your body gets used to it. Common complaints are tiredness, paleness, shortness of breath on exertion, palpitations, headache and cold hands and feet. Some women also get brittle nails or hair loss.

These complaints are not specific to anaemia and can have other causes too. That is exactly why a blood test is useful: it objectively shows whether your iron stores and haemoglobin are at the right level.

Do you stay tired despite enough rest, and do you menstruate heavily? Then that is a good reason to look further.

Which blood values do you test?

When anaemia from blood loss is suspected, three values matter most: haemoglobin, ferritin and MCV. Together they show whether you have anaemia, how large your iron stores are and which type of anaemia is likely. The table below lists them.

Ferritin is often the first value to drop, before your haemoglobin falls below the limit. That is why ferritin is so valuable with heavy menstrual blood loss. Ferritin can be temporarily raised during inflammation, so a single value does not always tell the whole story.

Note that reference values can differ per laboratory. The exact cut-off values and units are always shown with your own result, so compare your result against the limits on your own report. You can read more about this value in our article on the ferritin level and what a low ferritin means.

What can you do about anaemia from menstruation?

The basis is twofold: replenish the iron stores and, if needed, address the heavy blood loss. You top up iron through food and sometimes through supplements, but do not start that on your own without knowing your values. Too much iron is not beneficial either.

The Voedingscentrum points to iron-rich food such as wholegrain products, legumes, green vegetables and meat. Vitamin C helps your body absorb plant-based iron better. If your period stays very heavy, it is wise to discuss that with your GP, because there are treatment options for it.

I cannot give personal advice here. What suits you depends on your values and your situation, and you decide that together with your GP.

Testing your own blood values

If you want to know whether your heavy period has affected your iron stores, you can have your values drawn at Lunara without a referral. The Iron Status test looks at your haemoglobin and ferritin, among other things, so you get a clear picture of your iron stores.

You order online, give blood at one of the more than 750 draw locations and your blood is preferably drawn in the morning. Every result is assessed by a BIG-registered doctor, so you know what your result means.

Testing yourself does not replace a visit to your GP. See it as a starting point for a good conversation.

Frequently asked questions

Can anaemia resolve on its own after menstruation?

If the blood loss stops and you get enough iron, your stores often recover slowly on their own. With a persistently heavy period you empty the stores again every month, and then addressing the cause is needed. Discuss this with your GP.

How quickly do your iron stores recover?

That differs per person and depends on how empty your stores are. Replenishing ferritin often takes weeks to months, even when your Hb is already normal again. A follow-up measurement shows whether your stores are truly topped up.

Do I have to be fasting for an iron test?

For haemoglobin and ferritin you usually do not have to be fasting. Some laboratories do advise having your blood drawn in the morning, because iron values fluctuate through the day. Your draw location will tell you what applies to you.

Is a low ferritin the same as anaemia?

No. A low ferritin means your iron stores are low, but your haemoglobin can still be normal then. Only when the stores are so empty that your Hb drops do you speak of anaemia from iron deficiency. Ferritin is therefore an early signal.

References

1. NHG and Thuisarts.nl. Anaemia from iron deficiency. Dutch College of General Practitioners.
2. Thuisarts.nl. I have heavy blood loss during my period. Thuisarts.nl.
3. Voedingscentrum. Iron and iron-rich food. Netherlands Nutrition Centre.

Every blood test result through Lunara includes a professional assessment by a BIG-registered doctor. Blood testing through Lunara does not replace a visit to your GP. For a diagnosis or treatment, discuss your results with your GP.