How Soon After Taking Iron Supplements Will I Feel Better?


Assuming that you’re actually iron deficient, the research I went over to write this post suggests it will take 8-12 weeks to resolve most deficiencies.

I’ll break down the research briefly in the rest of this post.

Note that if you’re not iron deficient, a supplement won’t do too much of anything for you (beyond a possible placebo effect).

The Best Case Scenario: A Minor Iron Deficiency

If you have a very small deficiency, you might start to feel better in days once you start taking a supplement.

Your body will immediately absorb as much iron from the supplements as possible, which may clear up minor symptoms, but you’ll still have a deficiency that needs to be cleared up.

However, it will take longer than a few days in most cases.

It also depends on additional factors:

  1. Severity of your deficiency – It’s common sense that a bigger iron deficiency will take longer to correct than a minor one. The more severe your symptoms are, the longer you should expect it to take.
  2. If you’re pregnant or menstruating – These are 2 challenges for women that make iron deficiency common in the first place. They make recovery slower too for the same reasons.
  3. Iron absorption depends on other nutrients – In particular, you should always consume vitamin C along with iron to maximize absorption. Most of the best supplements also include vitamin C.

The Worst Case Scenario: A Significant Iron Deficiency

Most studies are done in people who are diagnostically iron deficient, and provide more realistic data to look at.

So let’s summarize the research now.

Study Link Dosage Results
Study 1 60 mg elemental iron per day 68% of women became non-anaemic after 8 weeks.
Study 2 100 mg elemental iron per day for 11-12 weeks The prevalence of anemia and iron deficiency decreased markedly
Study 3 1.35 g of oral ferrous sulphate (equates a few hundred mg of elemental iron) Girls in the study had significantly improved test scores after 8 weeks.

So for most people with an iron deficiency, you’ll see significant improvements within 8-12 weeks with a daily dose of 60-100 grams of elemental iron.

That iron doesn’t seem to be paired with vitamin C, so you may need even less.

How Much Iron Should You Supplement?

Most supplements will be in the form of elemental iron in case you were wondering.

It can be tempting to supplement in extremely high doses, but that can be dangerous.

Iron poisoning is a real possibility, especially in children/smaller adults.

Never go above 20 mg of iron per kg of body weight. That’s a limit of 900 mg of iron per day for a 100 lb (45 kg) person.

In reality, you should never get close to that. We’ve seen that even in studies, medical professionals only use 60-100 mg of iron per day.

Most supplements have 18-30 mg per serving, so you’ll likely want to take 3-4 per day if you have a significant deficiency.

If you need help finding a good supplement, I’ve written a detailed guide to the best plant-based iron supplements that you may find useful.


This is the part where I urge you to go see a doctor if you haven’t if you think you have a deficiency.

They can quickly test your hemoglobin and possibly identify if there are any other causes of a deficiency besides a lack of iron in your diet.

If you have any other questions, just leave them in a comment below.

About the author

Dale C.

Your friendly neighborhood vegan from Toronto. Chemical engineer turned semi-professional soccer player and freelance writer. Trying to do my small part in making the world better by writing about the wonderful world of veganism.