Weakness in an arm or leg that comes on suddenly is an emergency until proven otherwise. It can be a stroke, even if it passes. Call 112 or 999 in Ireland, 999 in the UK or 911 in the US.
Weakness that builds up slowly has many other causes, and most are not emergencies. A trapped or squashed nerve is common. Carpal tunnel syndrome can make your grip weak, so you drop things. A slipped disc in the back can weaken a leg, and wear in the neck can weaken an arm.
Any new weakness that lasts, keeps coming back or is getting worse needs a GP appointment. This page covers loss of strength. For tingling, see pins and needles. If your foot catches or slaps when you walk, see foot drop.
Get help now
Call 112 or 999 in Ireland, 999 in the UK or 911 in the US if you or someone else suddenly has:
Also call for sudden weakness or numbness down one side of the body, even if it has stopped. Do not drive yourself.
Also call 112, 999 or 911, or go to an emergency department, if weakness comes with:
Get an urgent GP appointment the same day (out-of-hours GP if needed, or NHS 111 in the UK) if:
See a GP if:
MedlinePlus separates two things. You may feel weak, but have no real loss of strength, for example with flu. Or there may be a loss of strength a doctor can measure. Weakness in one area is more noticeable, and more often has a specific cause.
If you feel drained all over, rather than unable to lift or grip, see our guide to feeling tired all the time. If one arm, hand or leg will not do what you ask, read on.
The HSE and NHS teach the FAST test: face, arms, speech, time. The arm sign is not being able to lift both arms and keep them raised, because one arm is weak or numb. Both also list weakness or numbness down one side of the body.
A TIA causes the same symptoms, but they pass. The NHS says they last a few minutes to a few hours and fully go within 24 hours. It says you cannot tell a TIA from a stroke in the early stages. The HSE and NHS both say you should see a specialist within 24 hours. Read about the FAST signs and stroke risk.
The HSE describes carpal tunnel syndrome as pressure on a nerve in the wrist. Symptoms include a weak thumb or difficulty gripping, numb hands, tingling and pain. They often start slowly, come and go, and are usually worse at night.
You are more at risk if you are pregnant, carry extra weight, have arthritis or diabetes, or often grip hard or use vibrating tools. A wrist splint worn at night can help. See a GP if symptoms are getting worse or home treatment is not working.
The HSE says sciatica can make the bottom, back of the leg, feet and toes feel painful, tingly, numb or weak. A slipped disc is the most common cause. Symptoms may be worse when you move, sneeze or cough. Sciatica usually gets better in 4 to 6 weeks.
The NHS lists muscle weakness among slipped disc symptoms. Both legs being affected is different. The HSE advises going to an emergency department, or calling 999 or 112, for the warning signs in the box above.
The NHS describes cervical spondylosis as a common condition causing neck and shoulder pain, often in people over 40. It is a normal part of ageing. The NHS advises an urgent GP appointment for heaviness or weakness in the arms or legs. It advises 999 for new problems walking, loss of bladder or bowel control, or sudden loss of co-ordination.
The NHS lists feeling more tired or weaker than usual, and muscle pain, among common side effects of statins. Do not stop a prescribed medicine yourself. Talk to your GP or pharmacist if you think a medicine is the cause.
This is damage to the nerves outside the brain and spinal cord. The NHS lists numbness and tingling, burning pain, loss of balance and muscle weakness, especially in the feet. The NHS says diabetes is the most common cause in the UK. We explain the causes worth looking for in peripheral neuropathy.
MedlinePlus lists an MS flare-up among causes of weakness in one area. The NHS lists numbness, balance problems and muscle stiffness among common MS symptoms. Symptoms may come and go. The NHS advises 999 for sudden weakness or numbness in one arm, as these could be signs of a stroke.
The NHS describes this as a rare long-term condition causing muscle weakness. Weak arms, legs or neck can occur, often with droopy eyelids, double vision or slurred speech. Symptoms tend to get worse when you are tired and better after sleep.
NHS inform, Scotland's health information service, describes functional limb weakness. It can cause problems walking, heaviness down one side, dropping things, or a limb that does not feel part of you. It can look like a stroke or MS, but scans show no damage to explain it. A specialist diagnoses it from specific features on examination. See our guide to functional neurological disorder.
MedlinePlus lists other causes of weakness. These include low blood sodium or potassium, an overactive thyroid, anaemia, muscle diseases and some poisonings.
This is not a way to diagnose yourself. It shows the details doctors find useful.
MedlinePlus says your doctor will ask when the weakness began, how long it has lasted and whether it is constant. They will ask about medicines and recent illness. If the weakness is in one area, the exam will focus on the nerves and muscles. Expect questions about:
MedlinePlus lists blood and urine tests, and imaging such as X-ray, ultrasound or MRI. For carpal tunnel syndrome, the HSE says nerve conduction studies may be used if the diagnosis is not clear. We explain what to expect in nerve conduction studies and EMG. You may be referred to a neurologist.
A weak grip from carpal tunnel syndrome is a common reason, especially with numb or tingling fingers. Other causes include nerve problems in the neck and, rarely, conditions such as MND or FND. If it keeps happening, see your GP. Sudden weakness in one hand is an emergency.
We could not find an NHS or HSE source that lists anxiety as a cause of one weak limb. Do not assume anxiety is the cause. Get it checked.
Yes. Treat it as an emergency. This can be a TIA, and the NHS says you cannot tell a TIA from a stroke early on. Call 112, 999 or 911. If it happened in the past and you never got it checked, contact your GP urgently.
Yes. The HSE lists weakness among sciatica symptoms, and a weak thumb or grip among carpal tunnel symptoms. The NHS lists weakness in the arms with neck problems. Most improve with time and treatment, but get any weakness checked.
This article is general information, not medical advice. It cannot diagnose the cause of your symptoms. If weakness comes on suddenly, call 112 or 999 (Ireland), 999 (UK) or 911 (US). Talk to your GP or pharmacist before starting, stopping or changing any medicine.
Reviewed by: Proco Team
Last updated: November 2026