What Causes Numbness In Left Arm and Hand?

Numbness in any part of the body is not a normal sensation, especially if it persists.

It can happen for many reasons but is commonly due to compression, irritation or damage to a nerve or the collection of nerves supplying an area of the body.

A gradual feeling of numbness in your left arm or hand is often harmless and will usually resolve on its own. If it occurs suddenly, frequently, is persistent, or you have other symptoms, you may need to seek medical care.


What Can Cause Left Arm Numbness?

1. Sleep Posture

One of the signs of a poor sleep posture is numbness in your hands when you wake up. This is due to the compression of the nerve that supplies your arm, causing your hands to become heavy and tingly. To prevent this, ensure you sleep on a comfortable mattress and use pillows.

2. Arm Injury

Numbness in your left arm may follow an injury to that limb. This is usually as a result of a fracture, specifically affecting the nerves or blood vessels. The extent of numbness is usually a function of the severity of the injury.

If you have suffered any injuries to your arm, you should seek medical care immediately. In cases of fractures, the ends of the bones must be placed contiguous to each other for healing to take place. Thereafter, movement around that area is limited until healing has taken place.

If there are any injuries to the nerves or blood vessels or in the case of major fractures, you may require specialist intervention and possible surgery.

3. Poor Blood Supply

Sometimes, blood vessels may be defective. This is often due to diseases such as hypertension, diabetes mellitus or kidney failure.


Sometimes, malformations and inflammation affecting these vessels may cause them to function below par. Associated symptoms could include pain, cold hands, and a color change in the limbs. It usually requires urgent medical care.

4. Slipped Disc

In our spines are soft pads lying between the bones of the spinal column called vertebral discs. When damaged, the vertebral discs can slip and impinge on the nerves in their path, causing numbness or weakness in the affected region. This is called disc herniation (or slipped disc).

When this happens in the neck, you tend to have numbness in your arms and hands. The discs may also be affected by other diseases, due to years of wear and tear, causing you pain and numbness. An example of this is cervical spondylolysis, a type of arthritis affecting the discs in the neck.

5. Burns

Following a burn injury, your left arm may be numb due to the direct effect of the burn injury or the response of your body to the injury.

In cases of heat or chemical burns that go beyond the skin layer, the nerves in that area may be destroyed directly. Also, the area of the burn may swell, causing compression of the nerves in your arm.


6. Alcoholic Degeneration

Excessive alcohol intake over a prolonged period may cause you to have some numbness in your hands. This is because alcohol may cause your reserves of minerals and vitamins – mainly vitamin B12, to become depleted.

These are necessary nutrients for your nerves. Apart from tingling in your left hand, you may experience weakness, fatigue or yellowness of your skin. You may also start having trouble walking or maintaining your balance.

7. Carpal Tunnel Syndrome

This is the compression of the median nerve that supplies the thumb, index and middle fingers and half of the ring finger.

In its journey, the nerve passes through a narrow passageway through the center of the wrist called the carpal tunnel. Sometimes, tissues around the median nerve may get inflamed, compressing the median nerve and causing numbness as it passes through the carpal tunnel.

It is commonly seen in people who do repetitive tasks around the wrist joint, such as typing. It is also common in pregnant women. In mild cases, medications are offered to help reduce symptoms. When severe or refractive to treatment, surgery is done.

A similar condition occurs higher up in the depression at the elbow region called cubital tunnel syndrome. The nerve affected here is the ulnar nerve.

8. Heart Attack

Numbness of the left arm may be one of the signs of a heart attack. This is because some nerves supplying the heart region are in the same area of the spinal cord as the nerves supplying the left limb. Thus, pain from the heart may be referred to the left arm, presenting as numbness.

Other symptoms of a heart attack are:

  • chest pain
  • shortness of breath
  • dizziness
  • neck, jaw or back pain

A heart attack is a medical emergency, you should call emergency services if you suspect you’re having one.

9. Other Diseases

These are diseases affecting nerves on the surface of the hand. These nerves can get progressively damaged, causing numbness.

For example, in diabetes mellitus, the nerves in a particular area of the body (more commonly the feet) become less effective, causing numbness due to the high level of sugar in the blood. This is called diabetic neuropathy.

If you have diabetes and have problems with sensation on your hands or feet, you should see your doctor. Other diseases that may cause numbness in your left hand include Multiple Sclerosis, Amyloidosis, HIV, Raynaud’s disease and Thyroid disease.

Some drugs are also able to cause nerve damage as a side effect, especially anti-cancer drugs.

10. Stroke

A stroke is caused by the interruption of blood supply to a part of the brain. When this happens, brain cells could be seriously affected within minutes. This can cause one-sided body weakness or numbness and other symptoms like:

  • speech problems
  • headache
  • inability to move limbs
  • dizzyness

When To See A Doctor

If you noticed numbness in your hands or arm after a night of uncomfortable sleep, it is likely from sleeping on your arm and should go away in a few minutes.

If you have a sudden onset or persistent numbness in your left arm or hand, you should see a doctor quickly. Also, you should see your doctor if you have additional symptoms like:

  • Loss of consciousness
  • Paralysis
  • Chest pain
  • Back or jaw pain
  • Shoulder pain
  • Confusion
  • A sudden and/or severe headache
  • A high fever
  • A swelling or fever
  • Difficulty talking


Many times, arm or hand numbness arises from nerve compression from sleeping or resting on your arm for a long period of time. It should go away after a few minutes.

However, if it is sudden, persistent has other associated symptoms, it could be a sign of something serious and you should see a doctor urgently.

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