Iron

Only when iron studies show you are low. In Canada, too much iron is about as common as too little.

At a glance

Our verdict	Only when iron studies (not ferritin alone) show you are low. Our products are iron-free by default.
Best use	Iron deficiency shown on blood tests
How sure the evidence is	Moderate for tiredness when stores are low
Cost a month	About $5 to $10

Written for adults in Canada. It explains the evidence; it is not advice for you personally. Last reviewed 20 October 2026.

Supplement Check

Is it right for you?

Iron is the supplement most likely to do harm when it is guessed. Whether you need it depends on iron studies read together, your periods, any family history of iron overload and your other medicines, and the cause of a shortage matters as much as the dose. Our Supplement Check looks at:

Haemochromatosis or iron overload in you: no iron, ever, and iron-free products only
A parent, brother, sister or child with haemochromatosis
Being a man, or a woman after menopause
Anaemia not caused by a lack of iron (B12 or folate deficiency, thalassaemia, sickle cell, haemolytic or aplastic anaemia)
Low ferritin without anaemia
Every medicine you take
The total across everything you already take, against the safe upper limits

Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.

$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check

Tell me when it opens

What it is

Iron is an essential mineral, found in red meat, legumes, tofu and leafy greens; vitamin C-rich food at the same meal helps it be absorbed. The body stores it as ferritin and carries it in the blood on transferrin.

We never choose an iron product automatically. Every iron line is held for Dr. French, who sets the dose and looks for the cause. All our other products are iron-free by default; prenatal multivitamins carry iron for pregnancy only.

Structure of Iron — Structure: PubChem (public domain).

How it acts

Iron is needed to make haemoglobin in red blood cells; when the stores run out, anaemia follows. Vitamin C increases how much iron is absorbed, which matters in iron overload. [1, 2] Our review did not cover how iron acts in more detail.

Outline of a person showing where Iron acts in the body

What it is used for, and what the evidence says

Iron is used to treat a measured shortage. Dr. French's rulings: test with iron studies, not ferritin alone; no iron for men or women after menopause without a test; all products iron-free by default.

Use	What the trials found	How sure we are
Tiredness with low iron stores and no anaemia	Iron improved self-rated tiredness by a small to moderate amount (standardised difference −0.38, where 0.2 is small and 0.5 moderate); fitness did not change. [3]	Moderate
ADHD in children with a low ferritin	23 children without anaemia and with ferritin under 30 µg/L, iron for 12 weeks (18 on iron, 5 on placebo): the ADHD rating score fell, but parent and teacher scales did not change significantly. [4] No trial in adults.	Very low
Ferritin alone as the test	At 30 µg/L, ferritin picks up 79% of iron deficiency and correctly clears 98% of people who are not deficient, in people seeking medical care. [5] But ferritin rises with inflammation and can hide a shortage; a transferrin saturation under 20% picked up 94% of shortages measured in the bone marrow, in heart failure. [6]	Low
Iron overload (haemochromatosis)	Iron and vitamin C supplements are to be avoided; brothers, sisters, parents and children should be screened. [1, 2] In people with two copies of the gene change, a transferrin saturation over 45% (women) or 50% (men) with a raised ferritin is enough for a provisional diagnosis. [2]	High (guidelines)

How sure we are: High means further research is very unlikely to change the answer; Moderate, it might; Low, it may well change; Very low, we are very unsure. These follow the GRADE method that guideline panels use.

Benefits

In a measured shortage: corrects it and the anaemia it causes.
With low stores and no anaemia: tiredness a little better (moderate certainty).
Without a shortage: no benefit, and a real chance of harm.

Risks and side effects

Stomach upset, which sets the upper limit of 45 mg a day. [7]
Iron overload. In people who already store too much iron, extra iron does harm. [1, 2]
The wrong treatment for the wrong anaemia. Anaemia from a lack of B12 or folate, thalassaemia, sickle cell disease and other causes needs a different treatment, and iron can do harm.
A missed cause. In men and in women after menopause, low iron needs a search for where it is being lost, often the gut. [8]

Interactions with medicines

Our sources list no effect of iron on how the liver clears medicines. Its interactions come from binding in the gut.

Medicine	What can happen	What to do
Levothyroxine, quinolone and tetracycline antibiotics, bone medicines (bisphosphonates)	Iron binds them and less is absorbed	Space by 4 hours; levothyroxine on waking, alone
Calcium, zinc	Compete with iron for absorption	Space the doses
Vitamin C supplements	Increase iron absorption	None in iron overload

Who should not take it

Haemochromatosis or iron overload in you: no iron, ever, and iron-free products only; no vitamin C supplements beyond what is in a multivitamin.
A parent, brother, sister or child with haemochromatosis: no iron product, and a ferritin and transferrin saturation test first.
Men and women after menopause: no iron without a test (Dr. French's ruling).
Anaemia not caused by a lack of iron (B12 or folate deficiency, thalassaemia, sickle cell, haemolytic or aplastic anaemia): no iron; book a consultation.
Low ferritin without anaemia: no iron product from the check; Dr. French reviews the cause.
Heavy periods with no recent iron result: iron studies first.
Pregnancy: prenatal iron only, within the 45 mg upper limit.
Under 18: outside the Supplement Check.

Dose and timing

No standard dose. Dr. French sets the dose from your iron studies and looks for the cause.
The test: iron studies (ferritin, iron, transferrin saturation) with C-reactive protein (CRP, a marker of inflammation), on the same blood sample, taken in the morning, with no iron tablet for 24 hours before.
How we read it: with CRP 5 mg/L or less, a ferritin under 30 µg/L is iron deficiency; with inflammation, a ferritin under 100 can still be deficiency; a transferrin saturation of 45% or more is possible overload and stops iron. [2, 9]
Count the iron in every product: the upper limit is 45 mg a day from all sources, and a prenatal plus an iron tablet can pass it.
Food first: red meat, legumes, tofu and leafy greens, with vitamin C-rich food at the same meal.
How to tell it is working: Dr. French decides when to repeat the iron studies.

What we know about Canadians

Too little. Iron deficiency in Canada is mainly a problem for women and girls who menstruate. In the national blood survey (2012 to 2019), 18% of women aged 19 to 50 and 21% of girls aged 14 to 18 had low iron stores, against 7% of the whole population; 6% had anaemia and 2% iron-deficiency anaemia. [10] About 30% of women 19 to 50 eat less iron than the average requirement. [11]

Too much. The opposite problem is just as common. In the same survey, 17.2% of Canadians had raised iron stores, mostly adult men, [10] and 21% of women after menopause had a ferritin over 150 µg/L. [12] The inherited form (two copies of the C282Y gene change) affects about 1 in 227 white North Americans. [13] That is why we do not put iron in a supplement for men or women after menopause without a blood test.

Most at risk of low iron: menstruating women and girls, heavy periods, pregnancy, no red meat, frequent blood donors. Of high iron: adult men, women after menopause, Northern European ancestry, regular alcohol.

How sure are we: high (shortage); moderate–high (overload). Measured, national and recent; a high ferritin also reflects inflammation, alcohol and fatty liver, not only iron.

An honest comparison: tiredness

The first step is finding the cause: sleep, sleep apnoea, mood, iron, B12, thyroid, alcohol and medicines. Cost a month in Canadian dollars.

Option	Effect	How sure we are	Cost a month (CAD)
Iron, only when ferritin is low without anaemia	Self-rated tiredness better (standardised difference −0.38); no change in fitness [3]	Moderate	About $5
Regular exercise	More energy and less tiredness against no treatment (effect size 0.37), but no effect against a placebo control [14]	Low	$0 to $21
None	No medicine is used for unexplained tiredness	—	—

If your iron stores are low, iron helps; if they are not, it will not.

Our verdict

Iron only when iron studies show you are low, at a dose Dr. French sets, with the cause looked for. Every other product we suggest is iron-free.

Never for anyone with haemochromatosis or iron overload, and never for men or women after menopause without a test.

In Canada about as many people have too much iron as too little, so guessing is not safe. Ferritin alone misleads both ways: inflammation pushes it up and can hide a shortage, and early overload can sit behind a normal ferritin. Dr. French's rulings are to test with iron studies, keep iron out of products by default, and give no iron to men or women after menopause without a test. When iron is low, it corrects anaemia, helps tiredness a little and is cheap; the care is in the testing and in finding the cause.