A heavy period is more blood loss than normal, often defined as flooding, large clots or a period that lasts longer than seven days. The main long-term consequences are a low iron and anaemia. Two blood values often give the most insight here: ferritin and haemoglobin.
I notice that many women do not know whether their period is heavy or not, because they have nothing to compare it with. That makes sense, because you only know your own experience.
Below you read when a period is truly heavy, what the causes can be, why iron is so important and which values give insight.
When is a period heavy?
A period is called heavy when you lose a lot of blood or when it limits your daily life. A handy guide is how often you have to change your protection and whether you flood, even with double protection. Large clots and a period lasting longer than seven days can also be part of it.
Signals that point to a heavy period:
- You change your protection every hour or more often
- You flood, even with double protection or at night
- You lose large clots
- Your period lasts longer than seven days
- You feel tired or dizzy around your period
If you recognise this every month, it is useful to look further, because prolonged heavy blood loss can deplete your iron.
What can cause a heavy period?
The cause of a heavy period ranges from hormonal swings to abnormalities in the womb, such as fibroids or polyps. Sometimes a clotting problem plays a part. Often there is no clear abnormality and it is a hormonal imbalance.
Possible causes at a glance:
- Hormonal swings, for example around perimenopause
- Fibroids or polyps in the womb
- A slow thyroid that affects the cycle
- A clotting problem, often present for a while
Which cause fits you depends on your age and your other complaints. Are you unsure about the broader context of your cycle? Then read our pillar on irregular periods and which hormones to test.
Why iron is so important with heavy blood loss
With every period you lose iron, and with a heavy period that loss can be bigger than you replace through food. So your iron stores can slowly fall, often without you noticing straight away. Complaints like fatigue, breathlessness or pale skin can come later.
A low iron can already give complaints before there is real anaemia. So it is useful to look at your iron stores alongside your blood. See also our article on iron deficiency without anaemia and what a low ferritin means.
Do you mainly feel tired and worn out? Then read which blood values to test for fatigue.
Which blood values give insight?
With a heavy period you mainly look at two values. Ferritin shows how big your iron stores are, and haemoglobin shows whether there is already anaemia. Together they give a picture of the impact of your blood loss.
- Ferritin, your iron stores, which often fall first
- Haemoglobin, which shows whether there is anaemia
The Iron Status panel maps your ferritin among other values. If you also want to look at your hormones, because your cycle is erratic too, the Hormones Women panel can help with that. You always discuss an abnormal result with your GP.
When do you go to the GP?
Go to the GP if your period limits your daily life, if you flood despite double protection, or if you have anaemia complaints such as ongoing fatigue or dizziness. Newly developed heavy blood loss is also a reason to have it assessed.
Get in touch in any case if you recognise this:
- Your blood loss limits your work, sport or social life
- You have ongoing fatigue, dizziness or breathlessness
- Your period has suddenly become much heavier
- You have bleeding between your periods
A blood test gives insight into the consequences, but the GP assesses the cause of the blood loss. So always discuss your result with a doctor.
Frequently asked questions
How much blood is too much during a period?
An exact amount is hard to measure in practice. A good guide is whether you flood, lose large clots or whether it limits your daily life. If you recognise that, it is useful to have it assessed.
Can a heavy period cause iron deficiency?
Yes, it can. With heavy blood loss your iron stores can slowly fall, sometimes without you noticing straight away. So it can be useful to have your ferritin and haemoglobin checked.
Which blood test do I do for a heavy period?
You often start with ferritin and haemoglobin to map the consequences for your iron. If your cycle is erratic too, a hormone test can give additional insight. Discuss with your GP what fits.
References
- NHG. NHG-Standaard Vaginaal bloedverlies. Dutch College of General Practitioners. Available via richtlijnen.nhg.org.
- Thuisarts.nl. I lose a lot of blood during my period. Dutch College of General Practitioners. Available via thuisarts.nl.
- Verdon F, Burnand B, Stubi CL, et al. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial. BMJ. 2003;326(7399):1124.
Every blood test result through Lunara includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
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