Medications

Iron Tablets Before Surgery

Iron tablets are one of the few things you're often told to keep taking before surgery, because a healthy blood count helps you cope with an operation. The main exception is bowel procedures, where iron can get in the way of the view.

Medically reviewed by Dr. Saurabh Shukla, MBBS, DNB Anesthesiology · Last updated June 2026

Quick answer

Iron tablets (ferrous sulfate, fumarate or gluconate) are usually continued before surgery — building up your blood count beforehand is a good thing and can reduce the need for a transfusion. The exception: they're often stopped about a week before a colonoscopy or bowel surgery, because iron darkens and sticks to the bowel lining and obscures the view. Confirm for your procedure.

Why it matters

Iron treats or prevents anemia (a low blood count). Going into surgery with a healthier blood level helps your body handle the operation and the blood loss that comes with it, and lowers the chance of needing a blood transfusion — so teams usually want you to keep taking it.

The one common exception is examinations and surgery on the bowel. Oral iron stains the lining dark and makes it sticky, which can hide small problems and make a colonoscopy harder, so it's paused for about a week beforehand.

If your iron level is very low, your team might top it up with an iron infusion (a drip) before surgery, which works faster than tablets — worth asking about if you're significantly anemic.

Do not stop without instruction

If you've been prescribed iron for anemia, don't stop it without checking — continuing it is usually exactly what helps you before surgery. Only stop if your team specifically asks (most often before a bowel scope or operation).

What to ask your doctor

Should I keep taking my iron, or stop it for this procedure?
Do I need to stop it before a colonoscopy or bowel surgery, and when?
Is my blood count high enough, or would an iron infusion help?
When do I restart afterward?

Red flags — call your team

Black stools are normal and harmless on iron tablets — but black, tarry, sticky stools with tummy pain or feeling faint can mean bleeding, so get that checked
Increasing tiredness, breathlessness or looking very pale before surgery — tell your team, your blood count may need checking

References

Reflects standard perioperative anemia management (e.g. patient blood management guidance); the colonoscopy/bowel exception is a practical bowel-prep consideration. Follow your team's instruction.

Frequently asked questions

Do I need to stop iron tablets before surgery?

Usually no — iron is generally continued because building up your blood count helps you cope with surgery and reduces the chance of needing a transfusion. The main exception is before a colonoscopy or bowel operation, where it's often stopped about a week ahead because it obscures the bowel lining.

Why stop iron before a colonoscopy?

Oral iron turns the bowel lining dark and makes it sticky, which can hide small lesions and make the colonoscopy harder to perform and interpret. Stopping it roughly a week before gives a clearer view. Your endoscopy unit will tell you exactly when to stop.

Are black stools from iron something to worry about?

On their own, no — iron tablets commonly turn stools black, which is harmless. What's different is a black, tarry, foul-smelling stool combined with tummy pain, dizziness or feeling faint, which can signal bleeding and should be checked. When in doubt, ask.

Could I get an iron infusion instead before surgery?

If your iron is very low or surgery is soon, an iron infusion (a drip) can raise your levels faster than tablets and is sometimes used before an operation. If you're significantly anemic, ask your team whether that's an option for you.

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