Numbness in Left Arm; 7 Common Causes & What to Do

Updated in April 2023

Numbness in the left arm may occur due to tendinitis or poor posture when sitting or sleeping. However, it may also be a sign of a more serious problem, like a heart attack, stroke, poor circulation or nerve compression from a tumor or infection. 

Feeling numb can lead to decreased sensitivity in the arm and hand, and it may be accompanied by other symptoms like chest pain, neck pain, difficulty breathing or frequent cramping.

In these cases, it is important to seek medical attention. The doctor may order testing to identify the underlying cause and to reach a diagnosis, which will then prompt appropriate treatment. 

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Main causes

Numbness in the left arm can be caused by: 

1. Heart attack

Numbness and and tingling in the left arm are one of the main symptoms of a heart attack. A heart attack can also cause other symptoms, like sharp or tight chest pain, general malaise, dry cough and difficulty breathing. Read more about the common symptoms of a heart attack

A heart attack occurs due to reduced blood flow to the heart, which, in most cases, is caused by a build up of fatty plaque within the blood vessels. Be sure to learn about what causes a heart attack so that you can prevent one in the future. 

What to do: If you suspect your symptoms are related to a heart attack, seek immediate medical attention or call 911. Treatment usually includes oxygen to facilitate breathing and medications that promote blood flow to the heart. Some patients may require cardiac catheterization, which involves inserting a stent or balloon into the affected vessels to restore blood flow and prevent tissue death. .

Following a heart attack, it is important for patients to engage in certain health measures, like regular exercise, smoking cessation, reduced alcohol intake and a healthy diet that is low in fried foods.  

2. Poor posture

Poor posture may be an important factor in the development of numbness and tingling in the left arm. Incorrect arm and spinal positions can lead to nerve compression that causes numbness. 

People who work on a computer, for example, may experience left arm numbness for frequently, particularly if their arms are not adequately supported. Poor sitting posture and incorrect height of the chair or desk can also lead to numbness. Work that requires frequent pressure on the shoulder or arm, like heavy delivery personnel or construction workers, may also experience numbness in the arms.

Sleep positioning and previous spinal problems may also lead to numbness in the left arm.

What to do: To improve posture and prevent left arm numbness, it is important to maintain a straight back and to distribute weight equally between both feet when standing. When sitting, you should ensure your lower back is supported in a chair and that your feet are flat on the ground. 

3. Tendinitis

Tendinitis is an inflammation of the tendons, which connect bones to muscle. This inflammation may emerge due to repetitive movements, like doing laundry, cooking or writing and typing for prolonged periods. These activities are associated with numbness and tingling in the arms due to frequent employment of the arms or elbows. 

In addition, patients may report arm weakness, difficulty moving and cramping. 

What to do: Tendinitis treatment usually involves anti-inflammatory medications, cold compresses 3 times per day for 20 minutes, and physiotherapy. You should also avoid heavy lifting and the movements or activities that triggered this condition.

4. Nerve injury or compression 

Some situations may lead to compression of back nerves, which can cause numbness and tingling that radiates to the arms. Health conditions that may lead to nerve compression or injury include tumors, spinal osteoarthritis, infection, staying in the same position for a long time or a cervical disc hernia.

What to do: In these cases, patients are advised to follow-up with a neurologist or orthopedic surgeon to identify the underlying cause of nerve compression. The doctor will perform a physical assessment and order image testing to reach a diagnosis. Nerve-related conditions are usually treated with physiotherapy, although surgery may be needed. 

5. Stroke

A stroke, or cerebral vascular accident (CVA) may also produce numbness or tingling in the left arm. Other common symptoms include an intense headache, weakness on one side of the body, garbled speech and loss of sensitivity. 

What to do: If you notice symptoms of a stroke, it is important to call 911 or to proceed immediately to a hospital for treatment. 

6. Peripheral neuropathy

Peripheral neuropathy is a disease that affects the peripheral nerves, which are located outside of the brain and spine. These nerves coordinate various bodily functions, like touch sensation, pain and muscular movements. This condition is often a consequence of diabetes, which is referred to as diabetic neuropathy in these cases. 

In addition to arm numbness, peripheral neuropathy can cause other symptoms like pain, burning, cramping and muscle spasms. 

What to do: Treatment for peripheral neuropathy should be oriented by a neurologist. The goal of treatment is to manage the underlying cause of this condition. Treatment may include medications, physiotherapy and, in some cases, surgery. 

7. Poor circulation

Poor circulation is characterized by the blood’s inability to flow freely through veins and arteries. This can occur as a result of built-up flatty plaques in the vessels, the presence of a clot or illnesses like diabetes. Poor circulation may also be a result of compression of the arm (while sleeping, for example).

In addition to arm numbness, other symptoms may also emerge, like tingling, cold finger tips, pale or blue skin, or swelling. 

What to do: Treatment for poor circulation should be oriented by a cardiologist, who may prescribe statins, aspirin, warfarin and/or antihypertensives. The type of medications prescribed will depend on the underlying cause of the poor circulation.