The first and most important thing you need to realise about iron and iron supplementation is that iron needs differ from person to person.

You might think that’s obvious, but if you were to Google “How long does it take for iron supplements to work?” you’ll mostly find specific answers like 2 weeks, 2 months, or even 2 years.

All of these may be true – because many factors come into play when determining when you should take iron, how iron is absorbed in your body, and how much iron you need.

That’s why today, we’ll examine each of them so you can make clearer, more informed decisions and achieve the results you’re looking for.

To start, let’s make a differentiation between how long it takes for iron to actually “work” and how long it takes for your body to “absorb” iron.

Active Iron consistently tops the charts as one of the best iron supplements on the market. An award-winning Irish brand, Active Iron tablets work quickly, and its Kind & Strong formulation is gentle on the stomach and is easy for your body to absorb.

How long does it take for iron pills to work?

It can take 2-3 weeks of taking iron supplements before a noticeable difference is felt. Depending on your iron needs, it may take up to 90 days to feel an increase in your energy. You may need to continue supplementing your dietary intake of iron to meet your body’s daily iron needs.

How Long Do Iron Tablets Take To Work: Iron Absorption

Iron is absorbed in the small intestine (like most nutrients), specifically the duodenum.

But how long it takes for an iron tablet to be absorbed, depends largely on when and how you take it.

When taking an iron supplement, the first stop along the tablet’s journey is the stomach, where the body’s stomach acid can oxidise the iron. This prevents the iron from reaching the mucosal sites of the duodenum in the small intestine, the body’s natural site of iron absorption.

Active Iron’s gentle formula remains in an easy to absorb state all the way through to the small intestine, thanks to its whey protein layer which helps protect the iron from stomach acid. Because of this, Active Iron is more likely to be absorbed than other oral irons on the market, decreasing the likelihood of side effects.

Your iron levels will begin to increase as soon as you start taking in more iron. But if you want to actually build up your intake and reap the benefits of iron supplementation, you’ll have to be a little more patient.

[Further reading: How iron is absorbed in your body]

How Long Does Iron Take To Get Into Your System After Taking Iron Tablets?

How long it takes for iron to get into your system depends largely on (1) why your levels were low in the first place and (2) how far below normal they were. The lower your current level, the longer it will take to build up a sufficient amount of iron in your system.

Consider the following cases:

    • If you need more iron because of menstruation, it will usually take a bit longer to build up because you’ll continue to experience blood loss with every period.
    • If your dietary intake of iron is insufficient, it may replenish very quickly if your supplement allows you to absorb it better.
    • If you change your current dietary habits to focus more on rich sources of iron, it might still take a while to get your iron levels back to normal.

ow long iron take to build up in your body

How Long To Take Iron Supplements? 

Achieving a noticeable benefit from iron supplementation may happen quickly, or may take some time to achieve, depending on several individual factors.

Those with a hectic, busy lifestyle, with little time to focus on selecting and consuming an iron-rich diet, may benefit from iron supplementation to ensure they maintain or increase adequate iron levels. For iron supplementation to work effectively, they need to be taken consistently.

If you find that you are not achieving optimal iron levels through diet alone, then you should continue taking an iron supplement even after you have rebuilt your iron stores, to ensure they do not dip again.

That being said, there are still a few vital factors you need to consider when you’re supplementing with iron.

Believe it or not, you can take a daily iron supplement and still not get the amount of iron you need – if your body is not absorbing it correctly. Let’s learn why that happens.

The Most Important Factors To Consider When Taking An Iron Supplement

Your current diet and nutritional habits

An iron-rich diet can be challenging to sustain, especially if you need to build up a significant amount of iron.

In this section, we are going to look at foods that decrease iron absorption, as well as foods that increase iron absorption.

Foods that decrease iron absorption

Some foods and nutrients are natural iron inhibitors – they diminish the absorption of iron and make it difficult for you to reach optimal levels.

These include:

  • Phytic acid (often found in grains and legumes)
  • Tannins
  • Polyphenols (found in tea)
  • Milk
  • Caffeine
  • Some of the proteins found in soybeans

(And, considering many people’s days start with a cup of coffee or a bowl of milk and cereal, we can quickly begin to see why iron absorption is a challenge.)

Foods that increase iron absorption

On the flip side, other foods are known for increasing your iron absorption, and they are often recommended to be taken alongside iron supplements. These include:

  • Citrus items and citric acid – lemons, lemonade, oranges, orange juice
  • Vitamin C
  • Vitamin A and beta-carotene (1)
  • Beef (2)
  • Meats, fish, and poultry (3)

How Soon After Taking Iron Supplements Will I Feel Better?

It can take anywhere from 8-12 weeks to feel better after taking iron supplements. You may feel better a few weeks after you start to take iron supplements. In some cases, it may take up to 6 months before you start to feel better.

In all cases if you suspect you need more iron, the best approach is to talk to a professional who can guide you and help you figure out the reasons you might not be feeling well and if iron is a factor in you feeling tired or fatigued. From there, they can guide you on whether iron supplements will help you feel better or not.

When Will My Iron Supplements Start To Work: Conclusion

If you want to reap all the benefits of optimal iron intake, you need to ensure you are absorbing iron well, and getting enough iron in your diet.

If your diet isn’t giving you enough iron, and you choose to supplement your iron intake, you will want to choose a supplement that provides optimum absorption and is kind to your stomach.

Active Iron supplements are designed with a unique formula. The protein layer acts as a barrier to the oxidising effects of stomach acid, making them more easily absorbed while also being gentle on your stomach. Active Iron is clinically proven to provide 2X better absorption of iron sulfate*, and its Kind & Strong formulation is 6X less likely to cause gut irritation**.

So if you want to know how long it will take for your iron supplements to work, remember this guide and  start taking Active Iron today.

How Long Does It Take For Iron Supplements To Work – FAQ:


How long does it take for iron supplements to work?

Iron supplements usually start working after 2 weeks, although some may need up to 6 months. The best way to know how long it takes for iron supplements to work is to test your blood levels. If they are below normal, then you should consider taking them.

How long should you take iron supplements?

Iron supplements should be taken for at least 6 months, and up to 12 months. The best way to ensure adequate absorption is to take them with food. If you do not take them with food, they may pass through your system too quickly.

How long do iron tablets stay in your system?

Iron tablets last for about three months after they are taken. However, if you stop taking them, then you may need to start again. If you don’t take them regularly, then your body won’t absorb all the iron from the tablet.

How long does it take for iron levels to drop?

Iron levels usually start dropping after about 2 weeks of stopping taking iron supplements. If you stop taking them suddenly, it may cause some temporary side effects such as headaches, nausea, diarrhea, constipation, dizziness, and irritability. However, these symptoms should disappear once you resume taking the supplement again.


*Wang et al. 2017, Acta Haematological, 138: 223-232
**Ledwidge et al. Data on file.