Ferrous sulfate

Iron supplements are among the most commonly taken things in any pharmacy, and they carry a warning most people read past. It is not boilerplate. The regulator wrote the sentence.

The exact words

Any dietary supplement in solid oral form containing iron as an iron source must bear this statement:

WARNING: Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6. Keep this product out of reach of children. In case of accidental overdose, call a doctor or poison control center immediately.

The regulation goes further than the wording. It says where the statement must appear: prominently on the information panel of the immediate container, not merely the outer box, and for unit-dose packaging in a way that keeps the warning intact until the last dose is used.

That level of specificity about placement is rare, and it exists because the failure mode is a bottle of sweet-coated tablets within reach of a small child.

Why a supplement gets a warning at all

Iron is an essential mineral. The dose that helps an adult with a deficiency and the dose that harms a toddler are not far apart, which is the whole of it.

That is a dose story rather than a hazard story, and it is the clearest example on this site of the distinction the guide to hazard and exposure draws. Nothing about iron is dangerous in the abstract. The quantity and the person decide.

The panel names the salt, which matters

Supplement labelling requires the source ingredient supplying a dietary ingredient to be identified, so an iron product prints something like Iron (as ferrous sulfate) rather than just iron.

That is worth reading, for a reason that is not obvious. The different salts carry different amounts of elemental iron per milligram of compound, so two products listing the same weight of salt are not delivering the same amount of iron. The panel states the elemental figure, and it is the smaller of the two numbers.

Ferrous sulfate, ferrous fumarate and ferrous gluconate are the usual three. The same source rule applies to Calcium carbonate, and the guide to a Supplement Facts panel covers what else that panel must disclose.

In fortified food

Flour and breakfast cereal are fortified with iron in many markets, often with reduced iron, which is finely powdered metallic iron rather than a salt.

Fortified food does not carry the poisoning warning, because the rule attaches to supplements in solid oral dosage form. The quantities involved are in a different range entirely, and a bowl of cereal is not a bottle of tablets.

During pregnancy

Iron supplementation in pregnancy is common and it is prescribed rather than guessed at, because the right dose depends on blood work rather than on a label.

What the label can give you is which salt, how much elemental iron, and what else is in the tablet. That is a useful thing to have in hand for the conversation, and it is where the page on reading labels during pregnancy draws its line as well.

One practical note that is a labelling fact rather than medical advice: antacids containing Calcium carbonate interfere with iron absorption, and both are extremely common during pregnancy. Whether that matters for you is a question for a pharmacist, who can answer it in about a minute.