Ferritin is a protein that stores iron inside your cells. A blood test measures the small amount that circulates in the blood, and doctors read that number as a marker of the body's iron stores. Only a blood test and a doctor can tell you whether your result points to iron deficiency, because the answer depends on the lab, your age and sex, and your other results.
This guide explains what the test shows, why reference ranges differ, and what to know before you buy an iron supplement. It is general information and does not replace medical advice.
What ferritin is and what the test shows
The body keeps spare iron bound to ferritin, mainly in the liver, spleen and bone marrow. When the stores shrink, less ferritin reaches the blood, which is why a ferritin test is often one of the first tests used to look at iron status. It is usually ordered together with haemoglobin and other blood counts.
Ferritin is also an acute-phase protein. It rises during infection, inflammation and some liver conditions, even when iron stores are low. A result that looks normal can therefore hide a shortage, and a high result does not always mean plenty of iron. That is why doctors often check an inflammation marker such as CRP next to it.
Why the "normal" ferritin level differs from lab to lab
Ferritin is reported in µg/L (the same as ng/mL). Each lab prints its own reference range on the result sheet, based on its method and the population it serves. Ranges differ for men and women and by age, and guidelines use different cut-offs when they define iron deficiency. For this reason we do not print a table of "normal" values: comparing your number with one from a website can mislead you in either direction.
A result inside the lab range does not mean there is no problem, and a result slightly below it does not mean you need a supplement. Read your number against the range on your own result sheet and ask your doctor what it means for you. Do not start iron on your own after reading a result.
Low or high ferritin: what the number does not tell you
Low ferritin. A low value says the stores are small, not why. Iron stores can fall because of low intake, higher needs (growth, pregnancy, regular blood donation), poor absorption or blood loss. Some of these causes need to be found and treated in their own right, so a supplement bought "to raise the number" can cover up something a doctor should look at.
High ferritin. A high value is not a reason to take iron. Besides iron overload it can reflect inflammation, liver problems or alcohol use, among other things. If your ferritin is high, do not take iron supplements unless your doctor tells you to.
Iron deficiency: why you cannot diagnose it yourself
Iron deficiency is a diagnosis made from blood tests and a doctor's assessment, often with more than ferritin alone. Everyday complaints such as tiredness have dozens of possible causes, so no list of symptoms can show that iron is the reason, and we deliberately do not give you one.
Some groups have higher iron needs: women who menstruate, pregnant women, regular blood donors, people who eat no meat and people with digestive conditions. NIH notes that recommended intakes for vegetarians are 1.8 times higher than for people who eat meat, because plant iron is absorbed less well. This is a reason to ask your doctor about a test, not a diagnosis.
Iron forms compared
If your doctor recommends an iron supplement, the label states elemental iron, so you do not have to calculate it. The compound it comes from differs:
| Form | Iron share by weight | Good to know | In our range |
|---|---|---|---|
| Ferrous bisglycinate (Ferrochel) | about 20% on the NOW label (18 mg iron from 90 mg chelate) | iron bound to glycine, an amino acid chelate | 18 mg and 36 mg |
| Ferrous fumarate | 33% (NIH) | iron salt of fumaric acid | 18 mg |
| Iron citrate | not stated on the label | iron salt of citric acid | 25 mg |
| Ferrous sulfate | 20% (NIH) | the form most often used in medicines | not stocked |
| Ferrous gluconate | 12% (NIH) | needs more compound per mg of iron | not stocked |
The EU health claims apply to iron in any form. What differs between products is the iron per dose, the directions and how your stomach tolerates it. Manufacturers describe the bisglycinate chelate as gentle, but head-to-head studies are few, so treat that as an expectation, not a promise.
The EU reference intake (NRV) for iron is 14 mg. Our products give 18 mg (128% of the NRV), 25 mg (179%) or 36 mg (257%). A higher number is not better. One 36 mg product is meant to be taken every other day, so read the directions, not only the milligrams. See all of them in the iron supplements collection.
How to take iron so it is absorbed better
Supplements contain non-haem iron, the same type as in plant foods. NIH describes what changes how much of it you absorb:
| Taken with | Effect | Practical habit |
|---|---|---|
| Vitamin C at the same meal | increases non-haem iron absorption | a glass of orange juice or fruit with the dose |
| Tea, coffee, red wine | polyphenols reduce absorption | keep them apart from the iron |
| Grains and legumes | phytates reduce absorption | do not rely on a bowl of porridge to carry the dose |
| Calcium (supplements, dairy) | may interfere, not firmly established | take at a different time of day |
| Zinc | 25 mg or more of iron can reduce zinc absorption | take at a different time of day |
| Some medicines | iron can interfere with levothyroxine and levodopa; acid-reducing medicines lower iron absorption | ask a pharmacist how far apart to take them |
Follow the directions on your pack, because they differ: some say with a meal, one is every other day. Pick a time that does not clash with your morning coffee and calcium, and stick to it.
Safety: too much iron, children and pregnancy
The body has no easy way to get rid of extra iron. NIH gives 45 mg a day as the upper limit for adults, counting iron from all supplements, including the multivitamin. Stomach upset, nausea and constipation are the common effects of ordinary doses, and very high doses are dangerous. People with hereditary haemochromatosis should not take iron supplements.
Keep iron supplements out of children's reach. NIH warns that iron swallowed by accident is especially dangerous for young children. If a child swallows iron, call 112 at once. Pregnant and breastfeeding women should take iron only as their doctor advises, and several products in our range say so on the label.
How to choose an iron supplement
- Get the blood test first and ask your doctor whether you need iron and how much.
- Find "iron" on the label and its % NRV. Compare milligrams of iron, not the weight of the compound.
- Read the directions: daily or every other day.
- Count the iron from every product you take, multivitamins included, and stay under what your doctor said.
- If your stomach is sensitive, ask your pharmacist about the form and the timing.
- Work out the price per day. If you avoid animal products, check whether the capsule shell is gelatin.
Swanson
Iron Citrate, 25 mg, 60 CapsulesWhat EU law lets us say about iron
Regulation (EU) No 432/2012 lists the authorised claims. They apply to products that provide at least 15% of the NRV (2.1 mg of iron) per daily dose:
- Iron contributes to normal formation of red blood cells and haemoglobin.
- Iron contributes to normal oxygen transport in the body.
- Iron contributes to the reduction of tiredness and fatigue.
- Iron contributes to normal energy-yielding metabolism.
- Iron contributes to normal cognitive function.
- Iron contributes to the normal function of the immune system.
- Iron has a role in the process of cell division.
These statements describe iron as a nutrient. They say nothing about ferritin levels or iron deficiency, and a supplement is not a substitute for a varied diet. If you also take other minerals, see our zinc and multivitamin ranges and count the iron in them.
FAQ
What is ferritin?
A protein that stores iron in your cells. The blood test measures the small amount in the blood, which doctors use as a marker of iron stores.
What is a normal ferritin level?
It depends on the lab, your age and sex. Use the reference range printed on your own result sheet and ask your doctor to interpret it, together with haemoglobin and, if needed, an inflammation marker.
Why can ferritin be low, and where does it "go"?
Stores fall when the body takes in less iron than it needs or loses more than usual. The test alone does not show the reason, which is why a doctor looks for the cause before anything else.
How do I raise my ferritin?
No supplement can promise a number. If your doctor finds that your stores are low, they will choose food changes, a dose and a repeat test. Iron from meat and fish is absorbed more readily than iron from plants, and vitamin C at the same meal helps with plant iron.
Can I take iron without a test?
We advise against it. You cannot tell from how you feel whether iron is the issue, extra iron is hard to remove, and a high ferritin result is a reason not to take it.
Can I take iron with calcium, tea or coffee?
These can reduce absorption, so take iron at a different time. Vitamin C can go with it.
Sources
- Regulation (EU) No 432/2012, authorised health claims
- Regulation (EU) No 1169/2011, Annex XIII (reference intakes)
- EFSA: Scientific Opinion on Dietary Reference Values for iron (2015)
- NIH Office of Dietary Supplements: Iron fact sheet for health professionals
Content reviewed by Inese Kalniņa, dietitian.
