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Causes of Arm Weakness & What to do About Right or Left Arm Weakness

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Last updated August 27, 2020

Arm weakness questionnaire

Use our free symptom checker to find out what's causing your weakness.

Arm weakness can limit the range of motion of your arm and affect your daily activities. Causes for weakness in arms include trauma from an injury, repetitive strain injury, nerve damage or compression in the neck or upper back, or blockage in the bloodstreams. Left arm weakness with chest pain may need immediate medical attention.

Arm weakness questionnaire

Use our free symptom checker to find out what's causing your weakness.

Arm weakness symptom checker

Arm weakness symptoms explained

Whether you're struggling to shampoo your hair or grab a heavy box from the garage shelf, arm weakness can be a concerning symptom. Arm weakness, sometimes called paresis or palsy, is the inability to raise your arms all the way up. It does not include being unable to move the arms at all, which is called paralysis. Depending on your accompanying symptoms, weakness in both arms is usually not as concerning as sudden weakness in just one arm.

Common characteristics of arm weakness

If you're experiencing arm weakness, it can likely be described by the following:

  • Objective weakness: This is muscle weakness that can be measured and verified by a medical provider.
  • Subjective weakness: This cannot be measured or verified by anyone else. You may experience this because you are "guarding" your arm, due to pain or injury. It can make you feel as though the arm is weak, even when it actually is not.

Common accompanying symptoms of arm weakness

Arm weakness may be accompanied by other symptoms, all on the same side of the body:

  • Severe headache
  • Mental confusion
  • Trouble speaking: Or with understanding speech
  • Numbness and weakness of face, arm, and leg
  • Vision trouble in one or both eyes
  • Dizziness, loss of balance, and trouble walking

Who is most often affected by arm weakness?

The following individuals are more likely to experience arm weakness:

  • Anyone with high blood pressure: High blood pressure puts you at risk for stroke, especially if you're also obese and/or a smoker.
  • Anyone with atrial fibrillation is at risk for stroke: One of the symptoms of stroke is one-sided arm weakness.
  • Anyone who works long hours doing repetitive physical work, or sports: You're at risk for damage, numbness, and weakness in one or both arms.
  • Newborns may have temporary weakness of one arm: This can be due to injury of the shoulder nerves during the birth process.

Are arm weakness symptoms serious?

The severity of arm weakness is ultimately dependent on the cause.

  • Not serious: Arm weakness following overuse, or heavy exercise such as weight lifting, will usually resolve with rest.
  • Moderately serious: Arm weakness along with pain in the neck or shoulder should be treated by your medical provider as soon as possible.
  • Serious: Sudden arm weakness with severe headache, along with difficulty moving or speaking, is a very serious symptom that must be treated right away.

What causes loss of strength in the arms?

Blockage or rupture of an artery in the brain

The blockage or rupture may cause severe symptoms that do not go away and must be treated immediately. The blockage may be temporary, or transient, and clear up on its own after a few hours or minutes. However, it should still be treated right away since it is a serious warning signal.

Injury-related causes

Injury to the arm — either abrupt or over time — can result in weakness.

  • Direct trauma: Trauma from a fall or an accident can cause localized nerve or muscle damage in the arm itself.
  • An overuse injury: An overuse injury, also known as a repetitive strain injury (RSI), can become permanent if not treated. It is caused by long-term damage to nerves, muscles, and tendons in the arm or shoulder from long periods of exercising the arm with the same motion. Simple fatigue from unaccustomed exercise can cause RSI, too.
  • Carpal tunnel syndrome: This is a form of overuse that can cause pain, guarding, and subjective weakness in the affected arm.

Nerve or disk damage

These conditions may cause pain in the upper back and neck. The arm may seem weak since you're trying not to use it, or are "guarding" it because it causes pain in the back and neck when moved.

  • A rupture or other damage to a cervical disk: This is the cushioning material between the bones of the spine.
  • Wear and tear of the bones and cartilage due to normal aging.
  • Crowding of the nerve roots in the neck: This can cause arm pain and weakness.
  • Arthritis in the spine: This may cause bone spurs which press on the nerves.
  • Narrowing of the spinal canal: This may cause pressure on the spinal cord.

Less common arm weakness causes

The following are less common causes of arm weakness:

  • Metabolic diseases
  • Neuromuscular diseases
  • Autoimmune disorders

Arm weakness questionnaire

Use our free symptom checker to find out what's causing your weakness.

Arm weakness symptom checker

Brachial plexopathy (shoulder nerve issue)

The brachial plexus is a web of nerves between the neck and shoulder, connecting the spinal cord nerves to the arm. There is one web on each side of the neck. Any injury that forces the shoulder to stretch down, and the neck to stretch up and away, can damage these nerves and cause brachial plexopathy.

Sports injuries and car accidents are often involved. Inflammation, tumors, and radiation treatment can also damage the brachial plexus.

Milder symptoms include numbness and weakness in the arm, with a shocklike stinging or burning sensation. A more severe injury can cause paralysis and loss of feeling in the arm, with pain in some parts of the arm, hand, and shoulder.

These symptoms should be seen by a medical provider since permanent damage can result if the injuries are not treated.

Diagnosis is made through electromyography (EMG) testing, CT scan, MRI, and sometimes angiogram.

Treatment usually involves rest and physical therapy. Surgery may be necessary to remove scar tissue or repair the damaged nerves.

Rarity: Uncommon

Top Symptoms: pain in one arm, shoulder pain that shoots to the arm, arm weakness, numbness in one arm, shoulder pain

Symptoms that never occur with brachial plexopathy (shoulder nerve issue): pain in the front middle part of the neck

Urgency: Primary care doctor

Repetitive strain injury of the upper arm

Repetitive strain injury of the upper arm is caused by consistent repetitive use.

Rarity: Uncommon

Top Symptoms: upper arm pain from overuse, upper arm weakness, upper arm numbness

Symptoms that always occur with repetitive strain injury of the upper arm: upper arm pain from overuse

Symptoms that never occur with repetitive strain injury of the upper arm: upper arm injury, severe upper arm pain

Urgency: Self-treatment

Pinched nerve in the neck

A pinched nerve in the neck is also called cervical radiculopathy. It means that a nerve in the neck, at a point where it branches off from the spinal cord, is being compressed by the surrounding bones, muscles, or other tissues.

It can be caused by a traumatic injury, such as from sports or an automobile accident, especially if the injury results in a herniated disk. It may also arise from the normal wear and tear of aging.

Symptoms include sharp, burning pain with numbness and tingling from the neck to the shoulder, as well as weakness and numbness into the arm and hand.

Diagnosis is made through patient history, physical examination, and simple neurological tests to check the reflexes. Imaging such as x-ray, CT scan, or MRI may be done, as well as electromyography to measure nerve impulses in the muscles.

A pinched nerve in the neck often improves with simply a few days or weeks of rest. Physical therapy, nonsteroidal anti-inflammatory drugs, and steroid injections into the spine can all be very helpful.

Rarity: Common

Top Symptoms: pain in one shoulder, spontaneous shoulder pain, pain that radiates down arm, pain in the back of the neck, severe shoulder pain

Urgency: Primary care doctor

Thoracic outlet syndrome

The "thoracic outlet" is the space on either side of the base of the neck where nerves, arteries, and veins travel beneath the collarbone. If these become compressed or damaged, the condition is called thoracic outlet syndrome or TOS.

The most common causes are trauma, such as a car accident or fall; and repetition or overuse, such as a sports injury.

Symptoms vary depending on the structures being compressed:

  • Neurogenic TOS affects the nerves. It is the most common form and creates numbness, tingling, pain, and weakness in the arms, hand, and fingers.
  • Vascular TOS affects the arteries and veins. It creates the same symptoms as neurogenic TOS as well as cold, pale hands and arms with weak pulse.

It is important to see a medical provider about these symptoms so that the damage does not become permanent.

Diagnosis is made through patient history, physical examination, imaging such as x-ray or ultrasound, and sometimes nerve conduction and blood flow studies.

Treatment involves physical therapy, pain relievers, and sometimes surgery.

Rarity: Rare

Top Symptoms: pain in one shoulder, spontaneous shoulder pain, arm weakness, arm numbness, pain in one shoulder blade

Urgency: Primary care doctor

Herniated (slipped) disk in the upper back

The backbone, or spine, is made up of 26 bones called vertebrae. In between the bones are soft disks filled with a jelly-like substance. These disks cushion the vertebrae and keep them in place. Although people talk about a slipped disk, nothing actually slips out of place. The outer shell of the disk ruptures, and the jelly-like substance bulges out. It may be pressing on a nerve, which is what causes the pain.A slipped disk is more likely to happen due to strain on the back, such as during heavy lifting, and older individuals are at higher risk.

Rarity: Common

Top Symptoms: upper back pain, neck pain, arm weakness, back pain that gets worse when sitting, upper spine pain

Symptoms that always occur with herniated (slipped) disk in the upper back: upper back pain

Urgency: Primary care doctor

Dislocated shoulder with nerve or artery damage

The shoulder is a ball and socket joint. This means the round top of the arm bone fits into the groove in the shoulder blade. A dislocated shoulder is when the entire ball is out of the socket. If the dislocation affects blood supply or a nerve, medical attention is extremely important.

Rarity: Rare

Top Symptoms: pain in one shoulder, arm weakness, shoulder pain from an injury, severe shoulder pain, arm numbness

Symptoms that always occur with dislocated shoulder with nerve or artery damage: pain in one shoulder, shoulder dislocation

Urgency: Hospital emergency room

Heart attack in a woman

A heart attack happens when the heart does not receive enough oxygenated blood to meet its demand, resulting in the death of heart tissue. This can be caused by a decreased supply of oxygenated blood or too high of a demand.

Symptoms include chest pain or pressure th...

Arm weakness questionnaire

Use our free symptom checker to find out what's causing your weakness.

Arm weakness symptom checker

Multiple sclerosis (ms)

Multiple sclerosis, or MS, is a disease of the central nervous system. The body's immune system attacks nerve fibers and their myelin covering. This causes irreversible scarring called "sclerosis," which interferes with the transmission of signals between the brain and the body.

The cause is unknown. It may be connected to a genetic predisposition. The disease usually appears between ages 20 to 50 and is far more common in women than in men. Other risk factors include family history; viral infections such as Epstein-Barr; having other autoimmune diseases; and smoking.

Symptoms include numbness or weakness in arms, legs, or body; partial or total loss of vision in one or both eyes; tingling or shock-like sensation, especially in the neck; tremor; and loss of coordination.

Diagnosis is made through patient history, neurological examination, blood tests, MRI, and sometimes a spinal tap.

There is no cure for MS, but treatment with corticosteroids and plasma exchange (plasmapheresis) can slow the course of the disease and manage symptoms for better quality of life.

Rarity: Rare

Top Symptoms: severe fatigue, constipation, numbness, decreased sex drive, signs of optic neuritis

Urgency: Primary care doctor

Stroke or tia (transient ischemic attack)

Transient ischemic attack, or TIA, is sometimes called a "mini stroke" or a "warning stroke." Any stroke means that blood flow somewhere in the brain has been blocked by a clot.

Risk factors include smoking, obesity, and cardiovascular disease, though anyone can experience a TIA.

Symptoms are "transient," meaning they come and go within minutes because the clot dissolves or moves on its own. Stroke symptoms include weakness, numbness, and paralysis on one side of the face and/or body; slurred speech; abnormal vision; and sudden, severe headache.

A TIA does not cause permanent damage because it is over quickly. However, the patient must get treatment because a TIA is a warning that a more damaging stroke is likely to occur. Take the patient to the emergency room or call 9-1-1.

Diagnosis is made through patient history; physical examination; CT scan or MRI; and electrocardiogram.

Treatment includes anticoagulant medication to prevent further clots. Surgery to clear some of the arteries may also be recommended.

Rarity: Common

Top Symptoms: dizziness, leg numbness, arm numbness, new headache, stiff neck

Symptoms that never occur with stroke or tia (transient ischemic attack): bilateral weakness

Urgency: Emergency medical service

Subarachnoid hemorrhage

A subarachnoid hemorrhage is characterized by a leakage of blood into the space between the first and second membranes surrounding the brain. The accumulation of blood causes the pressure inside the skull to increase, which can lead to brain damage and death.


When and how to treat arm weakness

When arm weakness is an emergency

Seek immediate arm weakness treatment in the emergency room or call 911 if the arm weakness is accompanied by:

  • Severe headache with weakness throughout one side of the body, including the face [7]
  • Total numbness in the arm with the skin appearing pale, blue, white or cold from loss of blood flow

When to see a doctor for arm weakness

You should schedule an appointment for:

  • Physical therapy: This can address the symptoms of repetitive strain injury [9].
  • Help with smoking cessation: Smoking is a huge risk factor for stroke and other illness [7].

At-home treatments for arm weakness

Remedies that you can try at home include the following:

  • Research additional equipment or modify your movement: Look into safety measures and equipment that can help you prevent or limit your chance of repetitive strain injury and overuse [9].
  • Address overall health: Make improvements in diet, sleep, and exercise, in order to maintain a normal weight, relieve stress, and lower blood pressure [16].
Hear what 1 other is saying
Fell down a stepPosted January 12, 2021 by A.
I fell down a step in September 2019 and badly injured my ankle. A few months later I started to feel a slight heaviness in my arm, which gradually got worse. had an MRI scan due to head pain, which raised my blood pressure. I paid to see a neurologist who said I had arthritis in my neck and that some of the nerves in my neck were too close to one another. I then saw a chiropractor who treated me for a trapped nerve and eventually the weight in my arm seemed to lessen. I then broke my back in late October, and since then my arm has become heavier than it was before. I don't know what's wrong with me but I would willingly pay for an operation to get it sorted. Any advice or help would be appreciated. Thanks for listening
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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