Muscle weakness: causes, red flags and when to seek help

Doctors separate three things that people often call weakness. True weakness is an objective loss of power that shows up on testing, such as difficulty lifting the arms above the shoulders or standing from a low seat. Fatigue is an overwhelming tiredness without a measurable loss of strength. Pain-limited movement is when you can produce power but stop because it hurts.

Describing exactly what you cannot do helps enormously. Trouble combing hair or reaching a shelf suggests weakness around the shoulders. Difficulty with stairs or rising from a chair points to the hips and thighs. A dragging foot suggests a nerve problem in the lower leg. Droopy eyelids, double vision or difficulty swallowing point to the nerve-muscle junction.

The NHS says the main symptoms of a stroke can happen suddenly and include face weakness, where one side of the face may droop and it might be hard to smile, arm weakness, where you may not be able to fully lift both arms and keep them there because of weakness or numbness in 1 arm, and speech problems such as slurring words or sounding confused. It describes this as FAST: face, arms, speech and time to call 999.

Other signs listed by the NHS include weakness or numbness down 1 side of the body, blurred vision or loss of sight in 1 or both eyes, difficulty speaking or thinking of words, confusion and memory loss, feeling dizzy or falling over, a severe headache and nausea or vomiting. It says to call 999 if you think you are having or have had a stroke, or have had signs of a stroke within the last 24 hours even if they have now stopped, and not to drive yourself.

The pattern of weakness helps locate the problem: brain, spinal cord, nerve roots, peripheral nerves, the junction between nerve and muscle, or the muscle itself. Symmetrical weakness of the hips and shoulders suggests a muscle problem, while weakness in one limb with sensory loss suggests nerve damage.

The NHS describes Guillain-Barre syndrome as a rare and serious condition affecting the nerves that needs urgent treatment in hospital, usually starting in the arms and legs with tingling, numbness or pins and needles in the feet and hands, followed by muscle weakness and difficulty moving the joints. Other symptoms can include nerve pain, problems breathing, drooping face muscles, trouble swallowing or speaking, and double vision. It advises an urgent GP appointment or NHS 111 if you think you have it, and 999 if you have drooping of one side of the face, trouble swallowing, inability to lift one or both arms or slurred speech, as these could be signs of stroke.

The NHS describes myasthenia gravis as a rare long-term condition causing muscle weakness, most commonly affecting the muscles controlling the eyes and eyelids, facial expressions, chewing, swallowing and speaking, but potentially most parts of the body. Symptoms include droopy eyelids, double vision, difficulty with facial expression, chewing and swallowing, slurred speech, weak arms, legs or neck and shortness of breath. It says symptoms tend to be worse when tired and better after sleep, and that severe breathing or swallowing difficulties need urgent hospital treatment.

Underactive thyroid can cause tiredness, weight gain, feeling cold, constipation and muscle symptoms, and the NHS says symptoms usually develop slowly. Some medicines, including cholesterol-lowering statins and long-term steroids, can cause muscle weakness or pain, and low potassium, low calcium and vitamin D deficiency can also contribute.

Call 999 for sudden face drooping, arm or leg weakness, slurred speech, loss of vision, confusion or severe headache, even if symptoms ease, as the NHS stroke guidance says.

From the NHS back pain page, call 999 or go to A&E for back pain with pain, tingling, weakness or numbness in both legs, loss of feeling around the genitals or anus, difficulty peeing or loss of control of bladder or bowels, or sexual changes. The NHS sciatica page adds sciatica on both sides, or severe or worsening weakness or numbness in both legs.

Weakness that is spreading upwards over days, causing difficulty breathing or swallowing, or leaving you unable to stand needs urgent hospital assessment. Dark urine with severe muscle pain after exercise, a crush injury or heavy drinking, which can signal muscle breakdown affecting the kidneys, also needs urgent care. Weakness after a tick bite, with a high temperature and stiff neck, or after an overdose, is an emergency.

The doctor will ask how quickly the weakness started, which muscles are affected, whether it is worse with activity or late in the day, whether there is numbness, pain, twitching or wasting, and about speech, swallowing, vision, breathing, bladder and bowels. They will ask about medicines, alcohol, recent infections or vaccinations, diet, family history and thyroid and diabetes history.

Examination covers muscle bulk and tone, power in each muscle group, reflexes, sensation, balance, gait and, for nerve-muscle conditions, eye movements and fatiguability. The NHS says in Guillain-Barre a GP checks reflexes and for numbness or weakness before referring to a neurologist, and that tests may include electrical nerve and muscle tests, breathing tests, blood tests and a lumbar puncture. Common first tests are blood tests for blood count, kidney function, electrolytes, calcium, thyroid, vitamin D, B12 and creatine kinase, followed by nerve conduction studies, electromyography, MRI of the brain or spine and spirometry as the picture dictates.

Keep moving within your limits, because inactivity itself causes muscle loss, and ask for a physiotherapy assessment if you are struggling. Eat enough protein and a balanced diet. Make the home safer to reduce the risk of falls, with good lighting, secure rugs and handrails where needed. Do not stop prescribed medicines because you suspect they are causing weakness; ask a doctor or pharmacist first.