Iron Fumarate vs Iron Sulfate
Two forms of the same compound. What differs is how much of it your body absorbs, how well you tolerate it and what it costs per month.
Side by side
Green marks the better value| Iron Fumarate | Iron Sulfate | |
|---|---|---|
| Absorption score | 25/100 | 20/100 |
| Elemental mineral | 32.9% | 20.1% |
| Cost per 100 mg delivered | $7.48 | $5.01 |
| Safety rating | 8/10 | 6/10 |
| Cost per month | $18 | $8 |
| Daily dose | 65-130 mg | 65-200 mg |
| Best timing | With food for comfort | Empty stomach if tolerated |
| Evidence level | A | A |
Verdict
Iron Fumarate wins on 3 of the measurable metrics.
It scores 25/100 against 20/100 on absorption, which is what decides how much of the dose actually reaches you. It does cost more per month — that is the trade-off.
What actually differs
Iron Fumarate
Well-tolerated iron form with good bioavailability and reduced digestive side effects compared to iron sulfate
- Better tolerance
- Good absorption
- Less constipation
- High elemental iron
- Higher cost
- Still some GI effects
- Drug interactions
- Less research than sulfate
Iron Sulfate
Most common and economical iron supplement form with high elemental iron content, standard treatment for iron deficiency anemia
- Highest elemental iron
- Lowest cost
- Most research
- Medical standard
- Digestive upset
- Food interactions
- Constipation
- Poor tolerance
What each form is for
Same compound, but the dose, the ceiling and the record differIron Fumarate — gentle iron with good absorption.
Usual daily dose 65-130 mg, taken with food for comfort. The ceiling is 45 mg a day (NIH ODS). It is named as the suspect product in 340 FDA reports. Evidence grade A.
Iron Sulfate — anemia treatment & iron deficiency.
Usual daily dose 65-200 mg, taken empty stomach if tolerated. The ceiling is 45 mg a day (NIH ODS). It is named as the suspect product in 340 FDA reports. Evidence grade A.
How these numbers are read
- The absorption score ranks forms of the same compound against each other. It is not a measured share of the dose — see how we derive it.
- Safety rating reflects tolerance at normal doses, not toxicity risk.
- Cost is per month at the typical daily dose, so a cheaper form taken at double the dose is not cheaper.
- Evidence level A means the form itself was studied, not just the parent compound.
Where to buy
Both forms deliver the same compound — pick by the numbers above, then check the label matches.
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Common questions
Which is better, Iron Fumarate or Iron Sulfate?
Iron Fumarate absorbs better — 25% against 20%. Absorption decides how much of the dose actually reaches you, so it usually matters more than the milligrams printed on the label.
What is the difference between Iron Fumarate and Iron Sulfate?
Both deliver the same active compound. They differ in how well the body takes them up, how they are tolerated and what a month costs: $18 against $8.
Can you take Iron Fumarate and Iron Sulfate together?
You can, but there is rarely a reason to. Two forms of the same compound stack the same active dose, so the usual approach is to pick the better absorbed one and dose it properly.