Iron Supplements poisoning in dogs and cats
Toxic agent: Elemental iron · Reviewed 2026-08-18
Phone a vet now, before reading on. Have ready: your pet's weight, roughly how much was eaten and when, and the packaging if there is any. ASPCA Animal Poison Control (+1 888 426 4435), Pet Poison Helpline, or Animal PoisonLine in the UK.
Iron tablets are corrosive on the way in and toxic once absorbed, and prenatal vitamins are the classic source — a bottle designed to be taken daily by a pregnant human is a serious ingestion for a dog.
What it actually does
Iron is directly corrosive to the gastrointestinal lining, which causes the early bleeding and vomiting. Absorbed iron then overwhelms the body's binding proteins, and free iron damages the liver, disrupts cellular respiration and causes cardiovascular collapse. Iron is not excreted efficiently, so it has to be chelated out.
How much matters
What counts is elemental iron, not tablet weight — the label states both and they are very different numbers:
| Under 20 mg/kg elemental iron | usually mild gastrointestinal upset |
|---|---|
| 20–60 mg/kg | serious toxicity expected |
| Over 60 mg/kg | potentially fatal |
| Ferrous sulphate 325 mg tablet | about 65 mg elemental iron |
| Prenatal vitamin | often 27–65 mg elemental iron per tablet |
Do the elemental arithmetic before panicking or relaxing — a 325 mg tablet is not 325 mg of iron. The vet will ask for the brand and strength.
What you will see, and when
Onset: Within 6 hours, often with a deceptive lull afterwards. Typical course: Several days; liver effects can appear late.
- 0–6 hoursVomiting, often with blood, diarrhoea, abdominal pain, lethargy
- 6–24 hoursAn apparent recovery that misleads owners into cancelling the appointment
- 12–96 hoursShock, liver injury, clotting problems, and later gastrointestinal scarring
What the vet will do
Vomiting may be induced early, but activated charcoal does not bind iron so it is not useful here. Abdominal radiographs can show the tablets, since iron is radiodense. Serum iron is measured, and deferoxamine chelation is used for significant exposures, alongside fluids and gastroprotection.
Outlook
Good if treated in the first phase. The lull is the trap — animals sent home during it can deteriorate badly.
Dogs and cats are not the same here
Both. Dogs raid bottles more often; cats are more likely to be affected by over-supplementation.
Where it comes from in a normal house
- Prenatal and postnatal vitamins
- Ferrous sulphate and ferrous gluconate tablets
- Children's chewable multivitamins with iron
- Some fertilisers and moss killers
- Oxygen absorber sachets in food packaging
The thing people get wrong
“Charcoal was given, so the poison is handled.”
Activated charcoal binds many toxins and iron is not one of them. Iron needs chelation, and radiographs to see how much is still sitting in the stomach.
PawLife keeps your pet's weight, medication and feeding history in one place, so when you make this call you can answer the vet's questions in seconds. The full food safety database is free.
Get PawLife on the App StoreFrequently asked questions
How much Iron Supplements is dangerous?
Do the elemental arithmetic before panicking or relaxing — a 325 mg tablet is not 325 mg of iron. The vet will ask for the brand and strength.
How long after exposure to Iron Supplements do symptoms start?
Within 6 hours, often with a deceptive lull afterwards. Vomiting, often with blood, diarrhoea, abdominal pain, lethargy. Several days; liver effects can appear late.
Is Iron Supplements worse for cats or dogs?
Both. Dogs raid bottles more often; cats are more likely to be affected by over-supplementation.
Is it true that: Charcoal was given, so the poison is handled.
Activated charcoal binds many toxins and iron is not one of them. Iron needs chelation, and radiographs to see how much is still sitting in the stomach.
Related emergencies
Sources
This page is information, not veterinary advice. Toxic doses vary with body weight, age, breed and individual sensitivity, and the figures above exist to explain what a vet is assessing, never to decide that an amount is safe. If you are reading this because something has already been eaten, call a vet.