Restless legs syndrome: causes, iron tests and treatment
Restless legs syndrome is a neurological sleep-related condition that causes an urge to move the legs, usually with uncomfortable sensations, worse at rest and worse in the evening or night. It is not just fidgeting, anxiety or "poor sleep hygiene". The useful approach is to confirm the pattern, check iron status and medication triggers, then treat the driver rather than escalating sedatives or dopamine drugs blindly.12
Key facts
- NHS guidance says restless legs syndrome causes a strong urge to move the legs, often with tingling, throbbing, itching or pain, usually worse at night when resting.1
- RLS can affect sleep, mood, concentration and quality of life. NHS guidance says to see a GP if it stops you sleeping, affects mental health or self-help has not worked.1
- Iron and dopamine pathways are central. The NHS says RLS is thought to be linked with iron levels and the brain chemical dopamine.1
- Current AASM guidance recommends checking ferritin and transferrin saturation, and suggests iron treatment thresholds that are higher than standard anaemia thresholds.3
- Dopamine agonists can help short term but can cause augmentation, where RLS starts earlier, spreads or becomes more intense over time. This is why newer guidance is more cautious.34
What RLS feels like
The classic RLS pattern has four parts. There is an urge to move the legs. It starts or worsens during rest, such as lying in bed, sitting on a sofa, driving or sitting through a film. Movement partly or completely relieves it, at least while movement continues. It is worse in the evening or at night than during the day. Some people describe crawling, pulling, aching, fizzing, electric or itchy sensations deep in the legs. Others mainly feel an unbearable need to move.
RLS often delays sleep because the moment you lie still, the symptoms rise. It can also wake you through the night or sit underneath insomnia: you might call it "bad sleep" before realising the legs are the reason. Some people also have periodic limb movements in sleep, where the legs jerk rhythmically without full awareness. A bed partner may notice this before the person with RLS does.
The severity range is wide. Mild RLS may appear after long flights, late caffeine or heavy training. Severe RLS can affect evenings every day, make sleep feel impossible, spread to the arms, and drive exhaustion, irritability or low mood. If RLS is making you feel unsafe, unable to cope or at risk of self-harm, seek urgent support through your GP, NHS 111 mental health option, 999 if life is at risk, or Samaritans on 116 123.
What it can be confused with
Not every leg symptom at night is RLS. The difference matters because treatment is different. Leg cramps are sudden painful muscle contractions, usually in the calf or foot, and may leave soreness. Peripheral neuropathy causes burning, numbness or tingling that may be present through the day and is not reliably relieved by walking. Akathisia is inner restlessness, often medicine-related, that can affect the whole body. Nocturnal anxiety can create agitation, but it does not usually follow the classic rest, movement and evening pattern.
| Condition | Typical clue | Useful next step |
|---|---|---|
| Restless legs syndrome | Urge to move, worse at rest and at night, eased by movement | Check iron status, triggers and medicines |
| Leg cramps | Sudden painful tightening of a muscle | Review hydration, electrolytes, medicines and muscle load |
| Peripheral neuropathy | Burning, numbness or pins and needles, often not relieved by walking | Check diabetes, B12, alcohol, medicines and nerve causes |
| Akathisia | Whole-body restlessness, often after antipsychotics or some antidepressants | Medication review is central |
| Sleep apnoea or insomnia | Fragmented sleep, snoring, pauses, racing thoughts or early waking | Assess sleep pattern rather than treating legs only |
Causes and triggers
Many people have primary RLS, meaning no single cause is found and family history is common. NHS guidance says RLS is more likely if someone in your family has it, and it can be linked with pregnancy, iron deficiency anaemia, kidney disease and some medicines.1 MedlinePlus similarly notes that anaemia, pregnancy, medicines, caffeine, tobacco and alcohol can contribute in some people.2
Iron is the big reversible cause to check. It is possible to have RLS-relevant low iron stores even before haemoglobin is low enough to call it anaemia. The 2025 American Academy of Sleep Medicine guideline states that consensus guidance suggests iron supplementation in adults with RLS when ferritin is 75 ng/ml or lower, or transferrin saturation is under 20 percent, and intravenous iron when ferritin is 75 to 100 ng/ml in appropriate cases.3 These thresholds are not the same as a standard "is this anaemia?" threshold.
Medicines can also trigger or worsen symptoms. Common suspects include some antidepressants, antipsychotics, sedating antihistamines, dopamine-blocking anti-nausea medicines and some sleep medicines. Caffeine, nicotine, alcohol, sleep deprivation and late intense exercise can make symptoms worse in some people. Pregnancy-related RLS often improves after birth, but pregnancy needs its own medication-safety discussion.
What to test
A useful GP review starts with the pattern: time of day, whether movement helps, which limbs are affected, sleep disruption, pregnancy, kidney disease, blood loss, heavy periods, diet, medicines, family history, neuropathy symptoms, cramps, diabetes risk, snoring, and daytime sleepiness. A sleep study is not needed for typical RLS, but it may be useful if sleep apnoea, periodic limb movements or another sleep disorder is suspected.
Ask specifically about iron testing. Ferritin alone is useful, but it can be misleadingly normal or high in inflammation because it is an acute-phase marker. The 2021 Mayo Clinic Proceedings algorithm recommends an iron panel including serum iron, ferritin, total iron-binding capacity and percentage transferrin saturation, measured in the morning after avoiding iron-containing supplements and foods for at least 24 hours where practical.4
Other tests depend on the story: full blood count, B12, folate, kidney function, thyroid function, HbA1c, inflammatory markers, pregnancy testing where relevant, and review of medicines or alcohol. If RLS starts suddenly, spreads to arms, is severe, appears with weakness or numbness, or is not fitting the classic pattern, a broader neurological or medical review is reasonable.
Evidence point: iron treatment should be targeted to measured iron status and the wider clinical context. Do not take iron indefinitely without testing, because excess iron can be harmful and low iron can be a clue to bleeding or malabsorption that needs explaining.
Treatment options
For mild or intermittent RLS, NHS self-help advice is a good start: exercise during the day, regular sleep timing, a dark and quiet bedroom, warm bath or heat pads, walking, stretching or massaging the legs during symptoms, mentally distracting activities, stopping smoking support, avoiding caffeine after midday, avoiding alcohol close to bedtime, avoiding large late meals, late strenuous exercise, screens right before bed and daytime naps.1
If ferritin or transferrin saturation is low for RLS, iron repletion may be the most rational treatment. A 2019 Cochrane review included 10 randomised trials and 428 participants, with nine trials in meta-analysis. It found that iron probably improves restlessness and RLS severity compared with placebo, although the evidence base was limited and study designs varied.5 Oral iron can take weeks to months and may cause constipation or nausea. Intravenous iron is specialist territory and depends on iron indices, severity, absorption and safety.
Medication choices have shifted. NHS guidance lists pregabalin or gabapentin, painkillers such as codeine or tramadol, medicines for sleep problems, and dopamine-increasing medicines such as co-careldopa or ropinirole for occasional use or if other medicines have not worked.1 The 2025 AASM guideline, however, gives strong recommendations for gabapentin enacarbil, gabapentin, pregabalin and intravenous ferric carboxymaltose in appropriate adults, and suggests against standard use of dopamine agonists and levodopa because of long-term harms, especially augmentation.3
That distinction matters in a GP appointment. Dopamine agonists can feel very effective at first, but augmentation can make symptoms start earlier in the day, become more intense, spread to the arms, or require higher and higher doses. The 2021 Mayo algorithm also highlights avoidance of exacerbating medicines, iron treatment, alpha-2-delta ligands such as gabapentin or pregabalin for chronic persistent RLS, and careful handling of dopamine agonist augmentation.4
| Option | Best fit | Trade-off |
|---|---|---|
| Trigger work and sleep regularity | Mild or intermittent symptoms | Useful but often not enough for severe RLS |
| Iron repletion | Low ferritin or low transferrin saturation | Needs testing, monitoring and investigation of why iron is low |
| Gabapentin or pregabalin class | Persistent RLS, pain overlap, insomnia, avoiding dopamine augmentation | Can cause sleepiness, dizziness, weight gain, mood effects and dependence risk |
| Dopamine agonists or levodopa | Selected cases, often short-term or specialist-guided | Augmentation, impulse-control problems, sleep attacks and withdrawal issues |
| Opioid medicines | Severe refractory RLS under specialist care | Dependence, sedation, constipation and prescribing governance |
A practical plan
Start with two weeks of pattern tracking. Record bedtime, caffeine, alcohol, exercise timing, medicines, symptom start time, whether movement helps, sleep disruption, periods or pregnancy context, and whether symptoms appear in arms as well as legs. This helps separate RLS from cramps, neuropathy, medication side effects and sleep apnoea.
Then make the first appointment specific. Ask for iron studies, not just haemoglobin. Bring a complete medicine list, including over-the-counter antihistamines, nausea medicines, antidepressants, antipsychotics, supplements and sleep aids. If mental health is affected, say so directly: sleep deprivation from RLS can make anyone feel frayed, and NHS guidance recognises that talking therapies may help when RLS affects mental health.1
The health library can help you compare RLS with iron deficiency, sleep apnoea, neuropathy, anxiety, thyroid disease and medication effects. Use start here to prepare your timeline, insights to challenge supplement claims, and the stack builder if magnesium, iron, antihistamines, sleep aids or painkillers are stacking up.
- Does my pattern fit RLS, leg cramps, neuropathy, akathisia, sleep apnoea or another cause?
- Can we check a full iron panel: ferritin, serum iron, transferrin saturation and total iron-binding capacity?
- Could any of my medicines, antihistamines, antidepressants, antipsychotics, alcohol or caffeine be worsening this?
- If treatment is needed, should we address iron and consider gabapentin or pregabalin before dopamine agonists?
- When should I be referred to sleep medicine, neurology, renal medicine or a specialist RLS clinic?
References
- NHS, 2025. Restless legs syndrome. link
- MedlinePlus. Restless Legs. link
- Winkelman JW, Berkowski JA, DelRosso LM, Koo BB, Scharf MT, Sharon D, et al, 2025. Treatment of restless legs syndrome and periodic limb movement disorder: an American Academy of Sleep Medicine clinical practice guideline. Journal of Clinical Sleep Medicine. link
- Silber MH, Buchfuhrer MJ, Earley CJ, Koo BB, Manconi M, Winkelman JW, 2021. The Management of Restless Legs Syndrome: An Updated Algorithm. Mayo Clinic Proceedings. link
- Trotti LM, Becker LA, 2019. Iron for the treatment of restless legs syndrome. Cochrane Database of Systematic Reviews. link
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This article is educational and does not constitute medical advice, diagnosis, or a treatment recommendation. Medication uses described as “off-label” are not licensed for that purpose in the UK and should only be considered under qualified clinical supervision. Always speak to your GP, pharmacist, or a registered specialist before starting, stopping, or changing any treatment. If you have severe or alarm symptoms - unintentional weight loss, blood in your stool, difficulty swallowing, persistent vomiting, a fever, or severe pain - seek urgent medical care.