Left arm numbness could be due to something as simple as sleeping position or as serious as a heart attack. In between are dozens of other potential causes. This applies to numbness in the right arm as well.

A temporary feeling of numbness in your left arm is usually no cause for alarm. It will likely resolve on its own. But if it persists or you have any doubt about the cause at all, it’s worth calling your doctor.

Seek emergency medical assistance if you also have:

  • chest pain and pressure
  • back, jaw, or shoulder pain
  • skin discoloration
  • swelling or infection
  • breathing or swallowing problems
  • confusion
  • sudden headache
  • facial palsy
  • nausea, vomiting
  • sudden balance and coordination problems

Continue reading to learn about some of the causes of a numb left arm.

Problems with your arteries and veins can interfere with the blood supply in your arms. Vascular disorders are more likely to occur if you have diabetes mellitus, high blood pressure, or kidney failure. They can also be due to injury, tumors, or other malformations.

In addition to numbness and tingling in your arms and hands, you might also have:

  • pain
  • swelling
  • abnormal coloring of the fingertips
  • cold fingers and hands

Treatment is dependent on the cause and may include pressure wraps or a surgical intervention to repair the affected blood vessel.

Bone fractures

Numbness of the arm can be the result of a bone fracture. You’re also likely to have pain and swelling.

The bones must be repositioned and your arm must be prevented from moving until it heals. How this is accomplished depends on the extent of the injury. Minor fractures can sometimes be treated with a cast or brace alone. Major breaks can require surgery to align and stabilize the bones correctly.

Burns

A heat or chemical burn on your arm could cause numbness. This is especially true of a burn that penetrates the skin and destroys nerve endings.

Minor burns can be treated at home with cool water or a cold, wet compress. If there is broken skin, you can apply petroleum jelly. Don’t use butter or topical steroid ointments because they can lead to infection. Cover the area with a nonstick bandage, and let blisters heal on their own.

Go to the emergency room if you have a large burn, have other health issues, or notice any symptoms of infection. For severe burns, call 911. Such burns can be life-threatening and require complex would care.

Insect bites

Insect stings and bites don’t affect us all the same way. Some people have severe allergic reactions and others experience only minor symptoms. These may include numbness or tingling around the affected area.

Take care of mild bites by washing the area and applying a cool compress. Over-the-counter antihistamine can help reduce itching.

Seek immediate medical attention if you have symptoms such as:

  • trouble breathing
  • swelling of the throat, lips, or eyelids
  • nausea, cramps, or vomiting
  • rapid heartbeat
  • faintness or confusion

Herniated disk

A herniated disk in your neck can cause numbness, weakness, and a tingling sensation in one arm. It can also cause radiating pain in the arm, neck, or shoulders.

It can be treated with rest, heat and cold applications, and over-the-counter pain relievers. If symptoms continue, see your doctor. Prescription medications or surgery may be needed.

Brachial plexus nerve injury

The brachial nerves run down the arms from the spinal cord in the neck. Injury to these nerves can interrupt messages from the brain to the arms, causing loss of feeling. This can also affect the shoulder, elbow, wrist, and hand.

Minor injuries can improve on their own. Severe brachial plexus injuries may require weeks or months of physical therapy. Surgery is sometimes needed.

Other nerve injuries

Overuse peripheral nerve injuries can cause pinched nerves that lead to numbness and pain in your arm or forearm. For example:

Most of these problems can be corrected by:

  • avoiding repetitive tasks
  • avoiding activities that involve pressure to the injured area
  • surgery

Cervical spondylosis

Cervical spondylosis with myelopathy, also called cervical spondylotic myelopathy, happens when the spinal cord in your neck becomes compressed (from degenerative arthritis in the neck). This can cause numbness, weakness, or pain in your arm. Other symptoms are neck pain and trouble using your hands or walking.

A neck brace or physical therapy may be sufficient. Otherwise, you might need medications or surgery.

Cervical spinal stenosis

Cervical spinal stenosis is a narrowing of the spine in your neck. This can be due to cervical spondylotic myelopathy. This can lead to numbness, tingling, and weakness of your arm. It can also affect the feet, urinary bladder, and bowel.

It’s treated with medications, physical therapy, and sometimes surgery.

Heart attack

For some people, numbness of the arm is a symptom of a heart attack. Among other symptoms are:

  • chest pain and pressure
  • pain in either arm, jaw, or back
  • shortness of breath
  • dizziness
  • nausea or vomiting

A heart attack is a life-threatening emergency. Call 911 without delay.

Stroke

A stroke happens when there’s an interruption in the arterial blood supply to part of the brain. Brain cells start to die within a few minutes. Symptoms typically affect one side of the body and can include numbness of an arm, leg, or the lower face. Other symptoms are:

  • speech problems
  • confusion
  • sudden headache
  • vomiting
  • dizziness, balance and coordination problems

Stroke requires urgent medical treatment.

A transient ischemic attack (TIA) is sometimes called a ministroke. The symptoms are the same, but the decreased arterial blood supply to the brain is temporary. You should still see your doctor right away.

Emergency treatment depends on the type of stroke. Blood flow to the brain must be quickly restored. Treatment may also include clot-busting drugs and/or surgery to repair blood vessels. A period of recovery and rehabilitation is involved.

Multiple sclerosis

Numbness and tingling are often part of the first symptoms of multiple sclerosis (MS). Numbness in your arm can make it difficult to lift or hold things well. MS interrupts the conduction of signals between the brain and the rest of the body. Some other symptoms are:

  • balance and coordination problems
  • fatigue
  • dizziness, vertigo

There’s no specific treatment for this symptom of MS. It may resolve when your flare-up subsides. Corticosteroids are often used to treat flare-ups, which can also help normalize sensation in your arm.

Vascular thoracic outlet syndrome

Sometimes, nerves or blood vessels that affect your arms become compressed. This can lead to numbness, tingling, and pain in your arms, hands, and neck. Your hands might turn pale blue or be slow to heal wounds.

Vascular thoracic outlet syndrome can be treated with medications and physical therapy. Surgery may be needed.

Peripheral neuropathy

Numbness in your arm could be a symptom of peripheral neuropathy. This means that there’s some damage in the peripheral nervous system. Arm numbness is one symptom of this condition. Others are:

  • tingling or burning sensations
  • muscle weakness
  • abnormal reactions to touch

Some of the more severe symptoms are muscle wasting, localized paralysis, and organ dysfunction.

Infections, diabetes mellitus, hormone or vitamin deficiencies, and toxins are among the causes for this condition. Treatment depends on the cause and can sometimes resolve the problem.

Vitamin B-12 deficiency

Peripheral neuropathy can happen when you don’t get enough vitamin B-12. You might also develop anemia. Other symptoms of nerve damage are:

  • numbness, tingling, or pain in your hands or feet
  • lack of coordination
  • sensory loss
  • general weakness

Treatment involves increasing B-12 in your diet with foods such as:

  • red meat
  • poultry, eggs, fish
  • dairy products
  • dietary supplements

Wernicke-Korsakoff syndrome

Wernicke-Korsakoff syndrome can also cause peripheral neuropathy. The syndrome is due to thiamine (vitamin B-1) deficiency. Symptoms include confusion, disorientation, and an unsteady gait.

It’s treated with thiamine replacement therapy, alcohol abstinence, and improved diet.

Migraine headache

A hemiplegic migraine is one that causes temporary weakness one side of the body. It can cause your arm to go numb or develop that “pins and needles” feeling. Migraine also causes one-sided head pain, nausea, and light sensitivity.

Migraines are treated with over-the-counter and prescription-strength medications.

Lyme disease

Numbness of the arm can be due to untreated Lyme disease. It can also cause shooting pains or tingling. A few other symptoms are:

  • skin irritation at the site of the tick bite, or bull’s-eye rash
  • headache, dizziness
  • facial palsy
  • tendon, muscle, joint, and bone pain

Lyme disease can be treated with antibiotic therapy.

Lead poisoning

Exposure to high levels of lead can cause numbness of the extremities. Some other signs and symptoms of acute lead poisoning are:

  • muscle weakness
  • pain
  • nausea, vomiting
  • metallic taste in your mouth
  • poor appetite, weight loss
  • kidney damage

Chelation therapy is used to remove lead from your system when lead poisoning is severe.

Here are a few tips for dealing with numb arms:

  • If you tend to have numb arms in the morning, try adjusting your sleeping position. A wedge pillow can keep you from sleeping on your arms.
  • When your arm becomes numb during the day, try performing some simple movements to improve circulation.
  • Avoid repetitive shoulder, arm, wrist, and finger movements. Try to disrupt the pattern by taking frequent breaks from these movements.

If arm numbness is interfering with your work or other daily activities, it’s a good idea to let your doctor check it out. Specific treatments depend on the cause. Treating the underlying condition may ease your symptoms.

Arm numbness can resolve itself in a matter of days or weeks. The long-term outlook depends on the cause. Talk to your doctor about your specific case.