LAB RESULTS

Iron and ferritin: who actually needs an iron supplement?

What ferritin and transferrin saturation show, who tends to run low on iron, why to test before taking it, hemochromatosis caution, and how to take iron so it absorbs and sits well.

The short version

Take iron only when a blood test shows you need it. The body has no regular way to get rid of extra iron, so it can build up.
Ferritin reflects your iron stores. The WHO cutoff for iron deficiency in healthy adults is below 15 µg/L, and a ferritin below 30 µg/L picks up most cases. Ferritin rises with inflammation, which can hide low stores.
People who tend to run low include those with heavy periods, plant-based eaters (who need 1.8 times as much iron), pregnant people (27 mg a day) and frequent blood donors.
If you or a close relative has hemochromatosis, avoid iron and vitamin C supplements unless your doctor advises otherwise.
Vitamin C helps iron absorb. Keep milk, calcium and antacids at least 2 hours away, avoid caffeinated drinks at the same time, and consider ferrous bisglycinate, which tends to be gentler.

What do ferritin and transferrin saturation tell you?

Ferritin shows how much iron you have in storage. Transferrin saturation shows how much of the iron-carrying protein in your blood is loaded with iron. Read together with hemoglobin, they give a clear picture of your iron status.

Low ferritin: the WHO defines iron deficiency in apparently healthy adults as ferritin below 15 µg/L (the same as ng/mL). Many clinicians use below 30 µg/L, which picks up about 92% of cases.
Ferritin with inflammation: ferritin rises during infection, inflammation and with age, so a normal-looking result can hide low stores. With infection or inflammation, the WHO cutoff moves to below 70 µg/L.
Transferrin saturation: below about 20%, alongside a low or borderline ferritin, supports iron deficiency.
High ferritin: in healthy adults, above 150 µg/L in menstruating women or 200 µg/L in men may signal a risk of iron overload and needs follow-up. A high transferrin saturation can point to hemochromatosis.

Low iron can also exist without anemia, so a normal hemoglobin does not rule it out.

Who tends to run low on iron?

The groups most likely to run low are people who lose blood regularly, people with higher needs, and people who absorb less iron from their diet.

Heavy or long periods: menstrual blood loss is a common reason. The RDA is 18 mg a day for women 19 to 50, compared with 8 mg for men.
Plant-based eaters: iron from plants is less available, so vegetarians and vegans are advised to get 1.8 times the usual amount.
Pregnancy: the RDA rises to 27 mg a day.
Frequent blood donors: in a large US donor study, 27% of women and 18% of men who donated often had no iron stores left at their final visit.

Why shouldn't you take iron without knowing your levels?

Because extra iron has nowhere to go. The body controls iron by how much it absorbs and has no regular way to excrete it, so iron you don't need can accumulate over time.

The adult upper limit is 45 mg of iron a day from supplements and food combined, unless a clinician advises more. Tiredness has many causes, and when iron really is low, the reason for it is worth finding with your doctor. Testing first also gives you a baseline to recheck after two to three months.

Keep iron supplements out of reach of children.

What about hemochromatosis and family history?

Hereditary hemochromatosis makes the body absorb too much iron. It is one of the most common genetic conditions in people of northern European descent, and most people with it carry two copies of the C282Y change in the HFE gene.

It can stay silent for years, so family history matters. Clinical guidelines recommend screening family members, particularly parents, siblings and children, of anyone known to have it. A high ferritin and high transferrin saturation are typical findings.

People with hemochromatosis may be told to avoid iron supplements and vitamin C supplements, since vitamin C increases iron absorption. If it runs in your family, talk to your doctor before taking either. Apiece's safety rules leave iron out for anyone who reports iron overload.

How can you absorb more iron from a supplement?

Take iron with vitamin C or a glass of orange juice, and keep it away from things that block it.

Iron is best absorbed on an empty stomach. If it upsets your stomach, a small amount of food is fine.
Milk, calcium and antacids: wait at least 2 hours between them and iron.
Coffee, tea and other caffeinated drinks: avoid them at the same time as iron. Tea and coffee polyphenols also reduce absorption.
Acid-reducing medicines: keep at least 2 hours between them and iron.
Prescription medicines: ask your pharmacist how to time iron with anything you take, including thyroid medicine.

In single-meal studies these factors have large effects; across a varied diet the effect of any one is more modest, and your own iron status influences absorption even more.

Which form of iron is gentlest on the stomach?

Ferrous bisglycinate tends to be easier to tolerate than common iron salts. Constipation, diarrhea and nausea are common with iron, and they are a common reason people stop taking it.

A 2023 meta-analysis of 17 randomized trials found that, in pregnant women, ferrous bisglycinate raised hemoglobin more than other iron supplements and caused about 64% fewer reported stomach and gut side effects. Evidence in other groups is more limited.

Dosing every other day is another option to discuss with your doctor. In a trial of 150 young women with low iron stores, 100 mg every other day reached the same ferritin as daily dosing at the same total amount, with fewer gut side effects.

Iron is not part of Apiece's daily foundation. When it is included, it is ferrous bisglycinate.

Questions

What ferritin level is too low?

The WHO defines iron deficiency in healthy adults as ferritin below 15 µg/L, and many clinicians use below 30 µg/L. During infection or inflammation, ferritin runs higher, so a cutoff of up to 70 µg/L may apply. Ask your doctor to interpret your result alongside hemoglobin and transferrin saturation.

Should I take iron if I feel tired?

Not without a blood test. Tiredness has many causes, and the body can't easily get rid of extra iron. A ferritin and transferrin saturation test shows whether low iron is the issue, and your doctor can help find the reason if it is.

Can I drink coffee or tea with iron?

Avoid them at the same time. Caffeinated drinks and the polyphenols in tea and coffee reduce iron absorption. Take iron with water or orange juice and keep milk, calcium and antacids at least 2 hours away.

Is ferrous bisglycinate better than ferrous sulfate?

It tends to cause fewer stomach and gut side effects. In pregnant women, trials found it raised hemoglobin more and caused about 64% fewer gut side effects than other iron supplements. Evidence in other groups is more limited.

Should I avoid iron if hemochromatosis runs in my family?

Talk to your doctor before taking iron or vitamin C supplements. Guidelines recommend screening close relatives of anyone with hereditary hemochromatosis, usually with ferritin, transferrin saturation and a gene test.

Sources

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*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This page is general information, not medical advice. Check with your doctor or pharmacist before starting a supplement, especially if you take medication, are pregnant or nursing, or have a health condition. Updated 2026-10-20.