Arm Numbness: What Are the Causes?

Arm numbness is often temporary and harmless. However, in some cases, it can be an important signal from your body. Which arm is affected, how long the numbness lasts, and whether other symptoms are present are key factors in understanding the cause.

What is nerve compression?

Nerves act like “electrical cables” that travel from the brain and spinal cord to your arm, hand, and fingers. Along the way, they pass through narrow areas such as the neck, shoulder, elbow, and wrist.

If these areas are affected by bone, disc, or joint problems, muscle spasm, swelling, or prolonged pressure, the nerve can become compressed. When a nerve is compressed, signals to the brain are disrupted, which you may feel as numbness, tingling, electric-like sensations, or weakness.

👉 Nerve compression is the most common cause of arm numbness and, in most cases, does not mean permanent damage.

Is there a difference between right and left arm numbness?

Right arm numbness is most commonly related to nerve compression, poor posture, or muscle-related problems.

Left arm numbness is also often nerve-related. However, if it is accompanied by chest pain, shortness of breath, or other concerning symptoms, it should be evaluated from a cardiac perspective.

Numbness alone usually does not mean a heart attack. Associated symptoms are what matter most.

Can stress cause arm numbness?

Yes. Stress and anxiety can lead to arm numbness. When you are stressed, your body remains in a constant “alert” state. Muscles tighten involuntarily, especially in the neck and shoulders, which can increase pressure on nearby nerves.

Stress can also speed up breathing, constrict blood vessels, and make the nervous system more sensitive. As a result, numbness or tingling in the arm or hand may occur.

Stress-related numbness usually:

• improves with rest
• may worsen at night
• does not cause permanent nerve damage

However, if it happens frequently, it should not be dismissed as “just stress” without proper evaluation.

What is carpal tunnel syndrome?

Carpal tunnel syndrome occurs when a nerve passing through the wrist is compressed. It typically causes numbness in the thumb, index, and middle fingers.

Patients often describe it like this:
“My hands go numb at night, I wake up with weakness in my hand, and I keep dropping things.”

Repetitive hand movements, prolonged computer use, pregnancy, thyroid disorders, and diabetes can increase the risk. When detected early, carpal tunnel syndrome can usually be treated without surgery. Adjusting wrist-straining habits and using a night splint often provide significant relief.

Can shingles (herpes zoster) cause arm numbness?

Yes. Shingles can cause arm numbness, and this is sometimes overlooked.

Shingles occurs when the virus that causes chickenpox reactivates years later and affects a nerve. When a specific nerve is involved, symptoms appear in the area supplied by that nerve.

With shingles-related arm numbness, you may notice:

• numbness and burning in one arm
• sharp, electric-like pain
• extreme sensitivity to touch

A few days later, a rash with fluid-filled blisters often appears in the same area. In some cases, pain and numbness begin before the rash.

👉 Shingles-related numbness is typically one-sided and follows a nerve pathway. Early diagnosis is crucial to prevent long-lasting nerve pain.

Why does arm numbness happen at night?

Arm numbness that wakes you from sleep is very common. Often, you may be lying on your arm without realizing it, or nerves at the wrist, elbow, or shoulder may be under pressure.

Carpal tunnel syndrome, cervical disc problems, and poor sleeping positions are the most common causes of nighttime numbness. If it improves when you change position, it is usually benign and does not indicate a permanent condition.

Can vitamin deficiencies cause arm numbness?

Yes. Vitamin B12 deficiency is an important and common cause of numbness in the arms and legs. When B12 levels are low, nerves are affected, leading to numbness, tingling, or burning sensations.

Other symptoms may include:

• fatigue
• balance problems
• memory difficulties
• burning or soreness of the tongue

Deficiencies of vitamin B6, folate, and vitamin D can also cause similar symptoms, although less commonly.

Can diabetes cause arm numbness?

Diabetes is a major cause of nerve damage. In long-standing or poorly controlled diabetes, diabetic neuropathy can develop.

This may lead to numbness, burning, tingling, or pain in the arms and legs. Diabetic neuropathy usually develops gradually and worsens over time. Good blood sugar control can slow its progression.

When should arm numbness be taken seriously?

You should seek medical evaluation if:

• numbness occurs frequently
• it lasts for several days
• you notice clear weakness in the arm
• it regularly wakes you from sleep
• it is accompanied by neck, shoulder, or chest pain
• you have diabetes, heart disease, or vascular disease

Seek emergency care immediately if:

• left arm numbness occurs with chest pain
• sudden numbness affects the arm, face, or leg (possible stroke)
• speech becomes slurred or difficult
• numbness is accompanied by fainting or loss of consciousness

How does arm numbness improve?

Relief depends on the underlying cause, but simple measures help many people:

• avoid staying in the same position for long periods
• take breaks from computer and phone use
• perform gentle neck and shoulder stretching exercises
• avoid sleeping on your arm
• protect yourself from cold

If nerve compression, vitamin deficiency, diabetes, or circulation problems are identified, treatment is planned accordingly.

Reference: https://pubmed.ncbi.nlm.nih.gov/7810463/