What causes restless legs at night?

Restless legs syndrome is thought to involve dopamine signalling in the brain, and low brain iron is one of the best-established contributing factors; iron is required to make dopamine. Other causes and triggers include pregnancy, kidney disease, peripheral neuropathy, certain medications such as some antidepressants and antihistamines, caffeine, alcohol, and a family history, since RLS is often inherited.

Does low iron cause restless legs?

Low iron is one of the most firmly established contributors to restless legs syndrome. Iron is a cofactor for the enzyme that produces dopamine, and reduced iron in the brain appears central to RLS. UK and international guidance recommends checking ferritin in anyone with restless legs, and correcting it where levels are low; often to a higher target than the standard laboratory range.

What ferritin level causes restless legs?

In restless legs syndrome, clinicians generally aim for a ferritin above roughly 75 micrograms per litre; considerably higher than the bottom of a typical laboratory reference range. This is why people with RLS are frequently told their iron is 'normal' when it is not optimal for their symptoms. Interpretation should be done by a clinician, as ferritin also rises with inflammation.

How do I stop restless legs immediately?

In the moment, movement is the only reliable relief; walking, stretching, or rubbing the legs. A warm or cool bath, and getting out of bed rather than lying still, often help. These manage the sensation but do not treat the cause. If it happens most nights, checking your ferritin and reviewing your medications is the more useful step.

When should I see a doctor about restless legs?

See a GP if restless legs disrupt your sleep most nights, are worsening, began during pregnancy, or started after a new medication. Ask specifically for a ferritin test. Also seek assessment if you have numbness, weakness or pain, which point towards nerve or circulation problems rather than RLS.

Restless Legs at Night: Causes

Restless legs syndrome is that irresistible urge to move your legs, usually with an uncomfortable crawling or fizzing sensation, that arrives when you are still and is worst in the evening. Movement relieves it. Lying down brings it back. It wrecks sleep, and it is far more than an irritation; it is a recognised neurological condition affecting a substantial minority of adults.

It is also one of the few symptoms where there is a specific, well-evidenced blood test worth asking for by name.

What restless legs actually is

RLS is diagnosed on the pattern, not on a scan. The recognised features are:

An urge to move the legs, usually with an unpleasant sensation
Triggered or worsened by rest and inactivity
Relieved by movement, at least partially, for as long as you keep moving
Worse in the evening or at night than during the day

If all four fit, that is restless legs syndrome. If you have pain, numbness, weakness or symptoms that do not care what time of day it is, something else is more likely and deserves assessment.

Why iron is central to it

Restless legs is thought to involve dopamine signalling in the brain, and this is where iron becomes important.

Iron is a required cofactor for tyrosine hydroxylase, the rate-limiting enzyme in dopamine production. Without adequate iron in the relevant brain regions, dopamine signalling is impaired. Post-mortem and imaging studies in people with RLS have consistently found reduced iron in specific brain areas, sometimes even when blood iron measures look acceptable.

The practical consequence is unusually clear-cut for a symptom this common: checking ferritin is standard practice in restless legs, and correcting low iron genuinely improves symptoms in a substantial proportion of people.

The number that matters

Here is the part most people are never told.

In restless legs syndrome, clinicians generally aim for a ferritin above roughly 75 µg/L; well above the bottom of a standard laboratory reference range, which in many UK labs starts somewhere around 15 or 30.

That gap is why so many people with RLS are told their iron is "normal" and sent away. A ferritin of 25 is inside the reference range and is not adequate if you have restless legs. The reference range describes the population; it does not describe what your symptoms need.

If you take one thing from this article: ask for the actual ferritin number, not the word "normal".

The other causes and triggers

Iron is not the whole story, and a proper assessment covers the rest.

Pregnancy. RLS is markedly more common in pregnancy, particularly the third trimester, and usually settles after birth. Iron requirements roughly double in pregnancy, which is very likely part of the explanation; another reason ferritin is worth checking rather than assuming.

Family history. RLS runs in families, and inherited cases often start earlier in life.

Kidney disease. RLS is common in advanced kidney disease and in people on dialysis.

Peripheral neuropathy and diabetes. Nerve damage can produce overlapping symptoms and sometimes coexists.

Medications. Several commonly used drugs can trigger or worsen RLS: many antidepressants (particularly SSRIs and SNRIs), sedating antihistamines, some anti-sickness drugs, and lithium. If your restless legs started within weeks of a new prescription, that is worth raising; do not stop a prescribed medicine on your own.

Caffeine, alcohol and nicotine. All can worsen it. Worth a genuine trial of reducing them rather than a token one.

What helps

In the moment. Movement is the only reliable relief. Walk, stretch, or massage the legs. A warm or cool bath helps some people. Getting out of bed beats lying still and fighting it.

Habits that reduce frequency. Regular sleep timing, moderate exercise earlier in the day (very intense late exercise can make it worse), and cutting evening caffeine and alcohol.

Address the cause. Check ferritin. Review medications with your GP. Manage any underlying kidney disease or diabetes.

Medication for RLS exists and is genuinely effective for severe cases, but it is prescribed and monitored by a doctor; some RLS drugs can worsen symptoms over time in a phenomenon called augmentation, which is exactly why this is not self-managed territory.

What to ask your GP for

Test	Why it matters in restless legs
Ferritin	The key test. Ask for the number, and note the RLS target is higher than the lab's lower limit
Transferrin saturation	Adds to the picture where ferritin is ambiguous
Full blood count	Checks for anaemia alongside iron stores
Kidney function	Kidney disease is an established RLS association
HbA1c or glucose	Diabetes and neuropathy overlap with RLS
Medication review	Several common drugs trigger or worsen RLS

A note on interpreting ferritin: it rises during inflammation, infection and some chronic conditions, so a reading can look reassuring while iron stores are genuinely low. If your ferritin looks acceptable but your symptoms fit, that is a conversation to have rather than a door to close.

If it turns out your iron is low

Correcting low iron in restless legs is worth doing properly, because the target is higher than usual and getting there matters.

Most people start with oral iron. It works for many, though it can take months to shift ferritin meaningfully and gastrointestinal side effects cause a lot of people to stop. Where oral iron has failed, is not tolerated, or where levels need correcting faster or higher than tablets manage, an iron infusion is the alternative; and there is reasonable trial evidence for intravenous iron improving restless legs symptoms in people with low ferritin.

That decision follows the blood test. It is made with a clinician, based on your ferritin, your symptoms and why you are deficient in the first place. Nobody should be recommending an infusion to you before anyone has measured anything.

Restless legs and never had your ferritin checked?

It's the one test guidance specifically recommends for RLS; and the target is higher than most people are told. Two minutes to see whether it's worth getting.

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When to see a doctor

Book an appointment if restless legs disturb your sleep most nights, if symptoms are getting worse, if they began in pregnancy, or if they started after a new medication.

Seek assessment sooner if you have leg pain, numbness, weakness, or symptoms present during the day regardless of activity; those point away from RLS and towards nerve or circulation problems that need looking at.

The short version

Restless legs at night is a recognised neurological condition with a genuine, well-evidenced link to iron. Ferritin is the test, the target in RLS is higher than the standard reference range, and being told "your iron is normal" without seeing the number is not an answer.

Check the number. If it is low, correcting it is one of the few interventions in this area with real evidence behind it.

Sources

NHS, Restless legs syndrome: restless legs syndrome is described as linked to iron levels and to dopamine, with iron deficiency anaemia listed among the associated conditions.
NICE CKS, Restless legs syndrome: the primary care pathway, including checking iron status as part of the assessment.
NHS, Iron deficiency anaemia: the NHS overview of symptoms, the full blood count used to diagnose it, and the pathway of establishing the cause before treating with iron tablets.

Medically reviewed by Dr Rukhsana Jabar ("Dr Ros"), GMC-registered doctor (GMC 7265326).

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Restless Legs at Night: Why It Happens and the Test Most People Never Get