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Can Iron Supplements Cause Insomnia? (Research Review)

by Dale Cudmore | Updated: Jan 02, 2023

There’s no real research that shows that iron supplements cause insomnia.

Similarly, while iron-deficiency anemia can cause insomnia, having high iron levels also isn’t a known cause of insomnia.

So while some people claim that they developed insomnia symptoms after taking iron tablets, there are a few other potential causes that we can look at besides the iron itself.

Is Insomnia a Side Effect of Too Much Iron?

While iron supplements are available over the counter, you shouldn’t take them without a good reason to, and ideally with a doctor’s approval. Research shows that they can have long term negative health effects due to having an inflammatory effect, although insomnia is not one of those side effects (1).

In addition, iron toxicity is fairly easy to develop, especially for those taking iron supplements (2).

The tolerable upper intake level can be exceeded with just a few tablets of certain iron supplements:

Common side effects of consuming too much iron are (3):

  • Upset stomach
  • Nausea
  • Constipation
  • Abdominal pain
  • Vomiting
  • Faintness

Some of these could of course cause sleep trouble, but you would notice those obvious symptoms first.

Two Ways That Iron Supplements Could Cause Insomnia

While I said there’s no direct research linking iron supplementation to sleep trouble, there are 2 potential ways that I could see it happening, although we need to connect the dots a bit.

First, research shows that too much iron can reduce zinc absorption and zinc concentration in blood (4,5). Zinc is an important mineral for sleep, and a zinc deficiency could contribute to insomnia symptoms.

Secondly, iron tablets can interact with certain medications and have an adverse effect on iron levels. This is a problem since there is research linking iron deficiency to insomnia. Just another reason why you shouldn’t take iron supplements without consulting a doctor, especially if you’re taking other supplements or medications.

SummaryWhile getting too much iron can cause serious health side effects, insomnia is unlikely to be one, especially the only one. However, there is a possibility of adverse effects on zinc and iron levels (if taking other medication) that might cause sleep issues, but it’s a bit of a stretch.

Other Causes of Insomnia From Iron Supplementation

If the iron itself isn’t likely causing insomnia, something else has to be.

There are 3 particular other causes that are most likely in my opinion.

A Reaction to a Particular Form of Iron

No iron supplement is just pure iron. It needs to be combined with an anion for chemical stability.

If you look on the ingredients label for an iron supplement, you will see which form it is.

A review of different iron supplements found that ferrous sulfate had the lowest incidence of adverse effects, while ferrous fumarate had the highest rate (6).

Also consider that there are often other ingredients in a supplement besides the iron. Side effects could be a result of a rare reaction to one of those.

SummaryIf an individual has an uncommon reaction to a particular iron supplement, the solution may be as simple as switching to a different brand that uses a different form of iron.

Other Events in Life With Coincidental Timing

Sometimes we develop sleep issues and we look for an obvious cause - something that we’ve done differently recently.

Taking a new supplement could be that cause, or it could just be a coincidence that is just on our minds.

Sudden insomnia is usually caused by stress, which could be from:

  • Job stress
  • Traveling
  • Relationships
  • Upcoming expenses
  • Health concerns
  • Exams, tests, etc.

A Nocebo Effect

Minds are a powerful thing, and what we believe often becomes reality.

The nocebo effect is the opposite of a placebo.

A nocebo effect is said to occur when negative expectations of the patient regarding a treatment cause the treatment to have a more negative effect than it otherwise would have

Maybe it’s the taste or smell of the iron supplement that for some reason you don’t like, and your brain is suspicious of it. It’s possible for that alone to cause some negative health effects like sleep trouble, or anxiety that then turns into sleep trouble.

Summary: Do Iron Supplements Cause Insomnia?

Without research showing one way or another, we can’t conclude anything 100%.

However, there doesn’t appear to be a common link between iron supplements and insomnia.

That doesn’t rule out edge cases of unexpected individual reactions.

In cases of insomnia, it’s always good to consult a doctor. They can run tests to narrow down the root cause, and also see if an iron supplement is even needed.


  1. Iron supplements: the quick fix with long-term consequences
  2. Iron Toxicity
  3. NIH: Iron Fact Sheet
  4. Competitive interaction of iron and zinc in the diet: consequences for human nutrition
  5. Iron and zinc interactions in humans
  6. Tolerability of different oral iron supplements: a systematic review

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.