Arm numbness can be an alarming symptom, but it’s not always as concerning as it seems. It’s usually caused by something harmless, such as sleeping in an unusual position. But it can also sometimes be a sign of a heart attack or stroke.
Heart attacks and strokes happen when the blood flow to the heart or brain is interrupted, which can quickly cause tissue damage. That’s why it’s so important to act fast. If you notice signs of a heart attack or stroke in yourself or someone else, call 911 immediately.
Heart attack symptoms to watch for include:
- chest pain or discomfort in the center or on the left side
- pain, numbness, or prickliness in one or both arms, the back, neck, jaw, or stomach
- shortness of breath
- unusual fatigue or exhaustion
- sudden nausea or vomiting
Stroke symptoms to watch for include:
- trouble speaking or understanding (confusion, slurring words)
- numbness or paralysis in the arm, face, or leg (usually on one side)
- trouble seeing out one or both eyes
- a sudden intense headache
- trouble walking, dizziness, and loss of coordination
When in doubt, call 911. When it comes to strokes and heart attacks, every minute counts.
Read on to learn more about the more likely causes of your arm numbness.
Your body’s circulatory system is responsible for moving blood around your body. It carries oxygenated blood from the heart to the body’s other tissues, delivers nutrients to your cells, and brings deoxygenated blood back to the heart.
When there’s a problem with your circulation, blood doesn’t flow properly to certain areas of your body. This can lead to numbness and tingling, especially in your arms or legs.
Poor circulation isn’t a condition, but a symptom of something else. If you don’t notice any other symptoms, you probably unknowingly have your arm in an unusual position that makes it harder for blood to reach it. Stretch your arm out and see if you regain sensation.
In other cases, poor circulation can be a sign of:
- Peripheral artery disease. Peripheral artery disease happens when your arteries narrow, reducing blood flow to your arms and legs. It can also cause cramping or pain in your arms and legs.
- Blood clots. Blood clots are small clumps of blood that can form anywhere in the body, including your arms and legs. They can be life-threatening when they form in the blood vessels of your brain or heart. Immobile blood clots generally won’t harm you but a blood clot in your arm could break off and travel to the brain or other organs.
- Diabetes. Diabetes increases your risk of developing poor circulation. Years of high blood sugar can damage blood vessels, reducing their ability to circulate blood.
- Varicose veins. Varicose veins are enlarged, often visible, veins. These damaged veins don’t move blood as well as non-varicose veins.
Peripheral neuropathy happens when there’s damage to the peripheral nervous system. This is a complex network responsible for sending information from your brain and spinal cord — which make up your central nervous system — to the rest of your body.
This damage can result in mild to severe symptoms, such as:
- exaggerated pain when touched
- burning pain
- muscle wasting
- major organ problems
What causes peripheral neuropathy?
There are several conditions that can cause damage to the peripheral nervous system, including:
- Diabetes. Diabetes is one of the most common causes of peripheral neuropathy. About 60 to 70 percent of all people with diabetes develop some form of neuropathy.
- Trauma. Broken bones, burns, and other injuries can all cause either temporary or permanent nerve damage.
- Repetitive motion. Repetitive motions can cause inflammation in the muscles, tendons, and other tissues. This inflammation can compress and damage nerves, leading to conditions like carpal tunnel syndrome, thoracic outlet syndrome, and cubital syndrome.
- Vasculitis. This condition happens when chronic inflammation causes the vessel walls to develop scar tissue, which interferes with normal blood flow to the nerves.
- Autoimmune diseases. Autoimmune diseases involve your immune system attacking your body’s own cell, which can lead to nerve damage. Examples of autoimmune diseases include lupus and rheumatoid arthritis.
- Vitamin deficiencies. The peripheral nervous system requires proper nutrition. Deficiencies — such as not getting enough vitamin B-12 or vitamin B-1 — can cause peripheral neuropathy.
- Medications. Certain medications, including several chemotherapy drugs, can damage the peripheral nervous system.
- Infections. Some viral and bacterial infections target nerve tissue and cause severe damage. These include hepatitis C, Lyme disease, Epstein-Barr, and shingles.
- Tumors. Cancerous tumors can grow on or around nerves, causing compression.
- Exposure to toxins. Exposure to toxins, such as lead, can cause nerve damage.
- Kidney problems. When the kidneys aren’t working properly, toxins build up in the blood. These toxins can damage nerve tissue.
Occasionally, numbness may be the result of a serious animal or insect bite. The bite of a venomous snake may cause numbness in the extremities. A bite from a rabid animal can cause rabies, which causes neurological symptoms in its later stages.
If you have a numb arm after being bitten or stung, seek emergency medical treatment. You can also read about first-aid essentials for bites and stings.
Other things that can cause arm numbness include:
- Multiple sclerosis. This is a disease of the central nervous system. It results in communication problems between your brain and the rest of your body, which can result in numbness.
- Degenerative disc disease. As you age, the discs of your spine, which act as shock absorbers, start to wear down. Degenerative disc disease can result in numbness and tingling in your arms and legs.
- Herniated disc. Sometimes, the discs of your spine can rupture and put pressure on a nerve root. In a herniated (or slipped) disc, if the disc presses on a cervical spinal nerve, it can cause arm weakness.
- Hemiplegic migraine. Hemiplegic migraines are a rare type of migraine that can cause numbness, especially along one side of your body. It’s often mistaken for a stroke.
Even if you’ve ruled out a heart attack or stroke, it’s always a good idea to follow up with your doctor if you have unexplained numbness in any part of your body. This is especially important if it doesn’t seem to go away once you change positions.
During your appointment, make sure to tell your doctor:
- when your symptoms started
- what you were doing when they started
- whether your symptoms come and go or remain constant
- whether you regularly do repetitive motions
- what makes the numbness better or worse
- if you recently started taking a new medication or supplement
- if you’ve recently been stung or bitten
- if you’ve had any recent major injuries
- if you have any medical conditions, even if they don’t seem related to your symptoms