Can low iron cause insomnia?

Yes, iron deficiency can lead to sleep disturbances including insomnia. It disrupts dopamine pathways in the brain and is strongly associated with restless legs syndrome, which often causes difficulty falling and staying asleep.

What ferritin level is too low for sleep quality?

Research suggests ferritin levels below 50 ng/mL are linked to poor sleep and symptoms like fatigue and restless legs. Many clinicians use this threshold when considering iron supplementation for sleep improvement.

Will iron supplements help me sleep better?

If your ferritin or iron levels are low, supplementation under medical supervision can significantly improve sleep quality. Multiple studies show reduced insomnia and RLS symptoms after iron repletion, even in non-anaemic individuals.

Should I take iron without a blood test?

No, iron supplements should only be taken after a confirmed deficiency via blood tests. Excess iron can be harmful and may cause liver damage, so it’s important to consult a healthcare provider first.

Iron Deficiency and Sleep: What Low Iron Does to Your Rest

Annie Wouters
May 18
5 min read

Sleep problems are incredibly common in the UK, with an estimated one in three people struggling to get a good night’s rest. While stress, screen time, and irregular routines often get the blame, there’s another culprit that is frequently overlooked: iron deficiency. Iron plays a critical role in our overall energy levels, neurological health, and sleep regulation, and when those stores run low, it can have serious consequences for your sleep quality.

This article explores the scientific link between iron deficiency (particularly low ferritin) and poor sleep, including symptoms like insomnia and restless legs syndrome (RLS). We’ll dive into key research studies that provide compelling evidence and explain what to do if you suspect low iron may be disturbing your rest.

Roasted Brussels sprouts in a black skillet with a wooden spoon, on a dark surface. Background features blurred kitchen items.

What Is Iron Deficiency?

Iron deficiency occurs when the body doesn't have enough iron to meet its physiological needs. The most common causes include inadequate dietary intake, blood loss (e.g. from menstruation or gastrointestinal issues), poor absorption (as in coeliac disease), and increased demand (such as during pregnancy or endurance training).

Iron is essential for making haemoglobin, the molecule in red blood cells that carries oxygen. But its importance goes well beyond energy and oxygen transport; iron also supports neurotransmitter synthesis, particularly dopamine, which is crucial for regulating sleep.

Low iron, especially when reflected by low ferritin levels (a measure of iron stores), has been repeatedly linked with disruptions in sleep architecture.

How Iron Deficiency Affects Sleep

Iron deficiency can interfere with sleep in several ways:

Restless Legs Syndrome (RLS): A neurological condition characterised by uncomfortable leg sensations and an urge to move them, particularly in the evening or at night
Sleep Fragmentation: Waking up multiple times during the night
Insomnia: Difficulty falling asleep or staying asleep
Daytime Fatigue: Feeling tired despite a full night's sleep

While fatigue is a classic symptom of anaemia, research shows that iron deficiency can cause significant sleep problems even before haemoglobin levels drop low enough to diagnose anaemia.

What the Research Shows

Numerous studies have explored the connection between iron deficiency and sleep quality. One of the most comprehensive was a 2020 systematic review published in Nutrients, titled "Iron Deficiency and Sleep/Wake Behaviors: A Review of Preclinical and Clinical Studies" (source). This review included 93 studies, 30 of which specifically focused on RLS.

Of those, 29 showed improvements in sleep after iron supplementation. The review identified several mechanisms linking low iron to poor sleep, including dopamine disruption, reduced oxygen delivery, and altered myelination.

Another key study, a 2020 randomised controlled trial in the Journal of Neurology, tested intravenous iron in people with RLS and low ferritin (<75 ng/mL) but without anaemia. The findings showed marked improvements in sleep onset, fewer awakenings, and overall better sleep quality in participants who received iron treatment.

A third study published in Sleep in 2023 explored how ferritin levels correlated with sleep disturbance in over 1,000 adults with fatigue and insomnia symptoms (source). Participants with ferritin under 50 ng/mL were significantly more likely to report poor sleep. After iron supplementation, more than 60% of these individuals reported improved rest.

Why Ferritin Is the Key Marker

It’s a common misconception that a normal haemoglobin level rules out iron deficiency. In fact:

Haemoglobin indicates current oxygen transport capacity
Ferritin reflects total iron storage, and it drops long before haemoglobin declines

This makes ferritin a more sensitive marker for identifying early-stage iron deficiency, particularly in those experiencing nonspecific symptoms like poor sleep or fatigue. Experts often cite ferritin levels below 50 ng/mL as a threshold for potential therapeutic benefit.

Women of childbearing age, athletes, people with coeliac disease or inflammatory conditions, and vegetarians/vegans are particularly susceptible to this pattern of low ferritin without anaemia.

When to Consider Iron Supplementation

Iron supplementation should always follow a blood test and medical advice. Unmonitored iron intake can lead to toxicity and harm.

If sleep quality is poor and symptoms like RLS, fatigue, or brain fog are present, it may be worth requesting a panel including:

Ferritin
Serum iron
Transferrin saturation
Total iron-binding capacity (TIBC)
Haemoglobin

Treatment may involve dietary changes, oral iron supplements, or intravenous iron depending on the severity and the individual's ability to absorb nutrients.

The Gut-Iron-Sleep Connection

Emerging research suggests a complex relationship between gut health, iron absorption, and sleep quality. The gastrointestinal tract plays a crucial role in iron uptake, meaning that individuals with gut conditions such as coeliac disease, inflammatory bowel disease (IBD), or dysbiosis may struggle to maintain healthy iron levels even with adequate intake.

Poor gut function can therefore contribute indirectly to sleep disruption by limiting iron absorption and promoting inflammation. Additionally, the gut microbiome influences

melatonin production and neurotransmitter balance, further impacting sleep regulation.

For more on this topic, read our guide on how gut health affects your sleep.

Final Thoughts

Iron deficiency is a silent but significant contributor to sleep disturbances. Unlike quick fixes such as melatonin or magnesium, addressing iron levels gets to the root of the problem in many people, especially those with underlying fatigue, RLS, or hormonal imbalances.

The evidence is increasingly clear: adequate iron stores are essential for restorative, uninterrupted sleep. If sleep issues persist despite good sleep hygiene and a healthy lifestyle, low ferritin might be the missing link.

Frequently Asked Questions About Iron and Sleep

Can low iron really cause sleep problems?

Yes, iron deficiency, especially when ferritin levels drop below 50 ng/mL, has been linked to a range of sleep disturbances. It affects dopamine transmission in the brain, which plays a crucial role in regulating the sleep and wake cycle. People with low iron may experience insomnia, frequent night waking, or symptoms of restless legs syndrome, particularly in the evening or at bedtime.

How do I know if my sleep issues are related to iron?

Can iron supplements improve sleep quality?

What is the best form of iron for sleep-related issues?

Are there other supplements that help with sleep?

Does gut health affect iron absorption and sleep?