What Causes Numbness in the Left Arm and Hand?

Paresthesia is a fairly common experience and does not always indicate a serious underlying health condition.

For example, many people associate left arm numbness and tingling with a heart attack. However, in most cases, left arm numbness related to cardiac events is accompanied by additional symptoms such as pain or pressure in the arm, chest, neck, or face.²

That said, if your symptoms are persistent or recurring (known as chronic paresthesia), certain nervous system conditions may be contributing to the problem.¹

Nerve Injuries

Injuries that affect the nerves in the left arm can disrupt communication between the brain and body, potentially leading to numbness or tingling sensations. One example is brachial plexus neuropathy, a condition involving damage to the network of nerves that extends from the spinal cord into the arms.¹

Brachial plexus neuropathy may cause pain in the shoulders and arms, numbness, and limited mobility. Contact sports, car accidents, and other traumatic injuries can contribute to this type of nerve damage.

Herniated Disc

A herniated disc occurs when the soft discs between the vertebrae become torn or ruptured. Risk factors associated with herniated discs include:

• Repetitive bending or twisting of the lower back
• Lifting heavy objects
• Smoking
• Physical inactivity

Although herniated discs most commonly affect the lower back, a disc located near nerves connected to the left arm may cause tingling or numbness in the arm.³

Treatment may include rest, pain management, muscle relaxants, and physical therapy to help support healing and mobility.³

Carpal Tunnel Syndrome

Carpal tunnel syndrome occurs when the median nerve, which travels from the forearm into the hand, becomes compressed at the wrist. Common symptoms include tingling, numbness, burning, and itching sensations in the hands and arms.

Carpal tunnel syndrome is more common in women and in individuals who perform repetitive hand and wrist movements, such as typing, sewing, or fishing. Treatment options may include splinting, medications, or surgery depending on symptom severity.

Cubital Tunnel Syndrome

Cubital tunnel syndrome occurs when the ulnar nerve becomes compressed near the elbow. This condition may cause numbness, tingling, and pain affecting the fingers, hand, forearm, and elbow, especially when the elbow remains bent for long periods of time, such as during sleep.

Treatment options vary based on symptom severity and may include:⁴

• Splints, elbow braces, or protective padding
• Anti-inflammatory medications
• Physical therapy
• Surgery

Multiple Sclerosis

Tingling and numbness in the left arm may also be an early sign of multiple sclerosis (MS), an autoimmune disease that affects the nervous system.⁵ MS damages the protective covering around nerve cells, interfering with communication between the brain and body.

Additional symptoms associated with MS may include:⁶

• Problems with balance and coordination
• Cognitive difficulties
• Visual disturbances
• Numbness and tingling sensations affecting different parts of the body

MS affects an estimated 1 million Americans and is more common in people assigned female at birth than those assigned male at birth.⁵

Most people are diagnosed between ages 20 and 40. Early diagnosis and treatment are important because untreated MS may contribute to complications such as:⁵

• Memory problems
• Difficulty walking or moving independently
• Bowel or urinary incontinence
• Sexual dysfunction

Although there is currently no cure for MS, treatment plans often include medications and physical therapy to help manage symptoms and slow disease progression.⁵

Diabetic Neuropathy

Nerve damage caused by diabetes is known as diabetic neuropathy. Chronically elevated blood sugar levels may damage nerves throughout the body, leading to symptoms such as numbness and tingling in the limbs.

Symptoms vary depending on the type of neuropathy present, but sensory changes in the hands, arms, feet, and legs are common.

Diabetic neuropathy affects more than half of people with diabetes, though carefully managing blood sugar levels with the help of a healthcare provider may help lower the risk of nerve damage.

If you’re wondering, “Why is my left arm tingling?” it’s important to understand that paresthesia is not always directly caused by nervous system disorders or diseases. Several other conditions may also contribute to numbness or tingling in the left arm.

Vitamin B12 Deficiency

Vitamin B12 is an essential nutrient that supports healthy nervous system function, so it’s not surprising that a vitamin B12 deficiency may contribute to paresthesia — a tingling or numb sensation that commonly affects the arms, hands, legs, or feet.⁷

The recommended dietary allowance for vitamin B12 is 2.4 micrograms (mcg) per day for most adults.⁸ Vitamin B12 is naturally found in many animal-based foods, including fish, poultry, eggs, meat, and dairy products. It’s also available as a dietary supplement for individuals who may not get enough through food alone.

Inadequate Blood Flow

If you’ve ever fallen asleep in an awkward position, you may have woken up with a pins-and-needles sensation in your left arm caused by temporarily restricted blood flow.

While this commonly occurs during sleep, inadequate circulation to the arms may also result from injuries or underlying health conditions such as:

• High blood pressure
• Diabetes
• Kidney failure

If poor circulation is contributing to tingling in your left arm, you may also experience pain, swelling, or coldness in the hands and fingers.

Hypothyroidism

An underactive thyroid, also known as hypothyroidism, may cause symptoms such as numbness, tingling, and painful pins-and-needles sensations that can affect the arms.⁹

Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormone and may also cause symptoms including:⁹

• Fatigue
• Cold sensitivity
• Weight gain
• Dry skin

Although hypothyroidism is not curable, it is often manageable with treatment. Healthcare providers commonly prescribe levothyroxine, a medication that helps replace missing thyroid hormone levels.⁹

Fractures

A fracture in the arm may cause inflammation, swelling, and pain that can place pressure on nearby nerves, leading to numbness or tingling sensations.

Additional signs of an arm fracture may include:

• A misshapen arm
• A visibly displaced joint
• Bleeding
• A protruding bone
• Limited arm mobility
• Inability to move the arm

If you suspect a fracture, seek immediate medical attention.

Stroke

One serious condition associated with tingling in the left hand or arm is a stroke. A stroke is a medical emergency that may cause sudden numbness in the face, arm, or leg, often affecting only one side of the body.¹⁰

A stroke occurs when blood flow to part of the brain becomes interrupted, leading to brain cell damage or death.¹⁰ If the affected brain region controls movement or sensation in the left arm, symptoms may appear on that side of the body.

In addition to numbness or tingling, stroke symptoms may include:¹⁰

• Sudden confusion
• Difficulty speaking or understanding speech
• Difficulty seeing in one or both eyes
• Difficulty walking, dizziness, loss of balance, or lack of coordination
• Sudden severe headache

If you or someone else may be experiencing a stroke, call 9-1-1 immediately so emergency medical responders can begin treatment as quickly as possible.

Many cases of paresthesia are short-term (transient paresthesia) and may go away on their own. [1]

However, if you’re experiencing chronic or persistent paresthesia, it’s important to make an appointment with your healthcare provider. Left arm numbness, tingling, and related conditions may indicate a more serious problem that could require comprehensive treatment. By performing physical and nerve examinations, your healthcare provider can offer a proper diagnosis and treat the root cause of the problem to reduce or eliminate your symptoms.

If you experience numbness or tingling in left arm accompanied by pain, seek emergency medical treatment immediately. Or, if your left arm goes numb suddenly, call 9-1-1 right away, as this is a warning sign of a stroke.

It’s normal to feel unnerved when something is amiss with your physical health. Taking a proactive approach through at-home testing can be the first step in pinpointing possible causes and creating a plan for a promising recovery.

With Everlywell, you can screen for common health conditions at home with a variety of tests designed to keep care affordable, convenient, and clinically accurate. Whether you test for nutritional deficiencies or thyroid conditions with our at-home thyroid test, Everlywell will also connect you to telehealth professionals and prescription services to help you make a steadier recovery.

Browse our at-home test collection and learn more about your physical health with Everlywell.