See how much iron women need each day for your life stage and diet, based on the same evidence as our iron guide. Iron is one to test for before you supplement.

Your daily iron target

18 mg / day

Recommended for menstruating women aged 19 to 50.

Test before you supplement: more iron is not better.

Figures follow our iron guide for women. Iron is one supplement worth testing for first: a ferritin test shows your stores, and taking iron you do not need offers no benefit and can harm over time. The upper limit from supplements is 45 mg unless your doctor advises more. This tool is information, not medical advice.

How it works

Enter your life stage and diet, and the tool returns the amount of iron women need each day.

The formula and sources

It uses 18 mg a day for women aged 19 to 50, 27 mg in pregnancy, and 8 mg from age 51, multiplied by about 1.8 for vegetarians because plant iron is absorbed less well. The safe upper limit from supplements is 45 mg. These figures come from our iron guide.

Assumptions

You are a generally healthy adult.
The figure is a daily intake target, from food and supplements combined.

Limitations

This shows how much iron to aim for, not whether you are low. Iron is one to test for before you supplement, because taking it when you do not need it brings side effects and no benefit.

When to see a doctor

If you have signs of low iron such as fatigue or breathlessness, ask for a ferritin blood test rather than starting iron on your own.

Primary sources

National Academies, Dietary Reference Intakes for Vitamin A, Vitamin K, Iron and other trace elements. The report of record for the US iron intakes this tool uses, including the tolerable upper limit and the higher target for vegetarian diets.

These are US figures. The UK recommendation for women of reproductive age is lower, so if you are following NHS advice, check the figure your own health service uses.

Calculator version 1.0. Figures and formula last checked 27 July 2026 against the sources above. This tool gives general information and does not replace advice from your own doctor.

Frequently asked questions

How do I know if I am low in iron?

A calculator shows how much to aim for, not your level. The way to know is a blood test. Ask for a ferritin test if you have symptoms.

Should I take an iron supplement?

Only if a test shows you are low, or your doctor advises it. Taking iron you do not need brings side effects and no benefit.

Why do vegetarians need more iron?

Plant iron is absorbed less well than iron from meat, so intake targets are roughly 1.8 times higher. Pairing plant iron with vitamin C improves absorption.

Do heavy periods raise my iron needs?

Heavy or long periods are a common cause of low iron in women and can mean you need more. See our iron guide.

Iron Intake Calculator for Women