What Causes Numbness in the Left Arm and Hand?

Medically reviewed by William Ross Perlman, PhD, CMPP on October 20, 2023. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Table of contents

• Nervous System-Related Causes of Left Arm and Hand Tingling or Numbness
• Other Possible Causes of Left Arm Tingling or Numbness
• What To Do If You Experience Numbness or Tingling in the Left Arm
• Find More Insights on Your Well-Being at Everlywell

The clinical term for numbness or tingling in any part of the body is paresthesia. Occasionally, individuals may describe this sensation as “cold,” “burning,” or a “pins and needles in left arm” feeling. [1]

Experiencing pins and needles in your left arm or tingling can indicate the normal functioning of your nerves has been impaired in that area. Nerve damage and nerve pain may be caused by physical nerve damage or pinched nerve compression, acute physical injury or trauma, or an underlying health condition.

If you’ve been experiencing persistent numbness or tingling in your left arm, or even arm pain, it’s important to familiarize yourself with conditions and disorders that cause this. Below, we’ll cover some possible explanations in the areas of nervous system dysfunction and other health conditions. [1]

Nervous System-Related Causes of Left Arm and Hand Tingling or Numbness

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

For instance, it’s commonly thought that left arm numbness and tingling is a symptom of a heart attack. However, in the vast majority of cases, left arm numbness caused by cardiac arrest is accompanied by symptoms like pain and pressure in the arm, chest, neck, or face. [2]

That said, if you find your paresthesia symptoms are persistent (chronic paresthesia), any of the following nervous system conditions may be responsible. [1]

Nerve Injuries

Injuries that affect the nerves in your left arm can interrupt messages from your brain and cause numbness. For instance, brachial plexus neuropathy is a type of nerve injury characterized by damage to the nerves that run down the arms from the spinal cord. [1]

Brachial plexus neuropathy can cause pain in the shoulders and arms, as well as numbness and limited movement.1 Contact sports, auto accidents, and other factors can result in this kind of nerve injury.

Herniated Disc

A herniated disc occurs when the soft “disks” between your vertebrae become torn or ruptured. Risk factors associated with this condition include:

• Repetitive bending or twisting of the lower back
• Lifting heavy objects
• Smoking
• Having a physically inactive lifestyle

It’s most common to have a herniated disc in the lower back. However, if you have one located near nerves that run through your left arm, it can cause your arm to tingle and feel numb. [3]

Herniated discs and the numbness they can cause are typically treated with rest, muscle relaxers, and pain medication if necessary. Your healthcare provider may also suggest physical therapy to help your spine heal. [3]

Carpal Tunnel Syndrome

Carpal tunnel syndrome occurs when the median nerve, which runs from the forearm to the palm of the hand, becomes pinched at the wrist. Tingling and numbness in the arms are common symptoms of carpal tunnel, as well as frequent burning and itching.

Carpal tunnel is more common in women than men, and in those who perform repetitive tasks with their hands and wrists, such as sewing, fishing, and typing. Healthcare providers may treat this pinched nerve compression with surgery or with non-surgical treatments, including splinting and prescription medications.

Cubital Tunnel Syndrome

Cubital tunnel syndrome results from the pinching of the ulnar nerve, which runs on the inner side of the elbow. This condition can cause numbness, tingling, and pain in the fingers, hand, forearm, and elbow, especially when the elbow is bent for a long period of time, such as during sleep.

Treatment options for cubital tunnel syndrome and ulnar nerve pinching depend on how severe your symptoms are. Milder cases may simply require rest or refraining from activities that worsen symptoms. More progressed cases may require treatment with [4]:

• Splints, elbow braces, or the use of elbow padding
• Anti-inflammatory medication
• Physical therapy
• Surgery

Multiple Sclerosis

A tingling and numb left arm may be an early sign of multiple sclerosis (MS), an autoimmune condition that impacts the nervous system. [5] This disease damages the material that surrounds and protects nerve cells, slowing down or blocking messages between your brain and body.

Related symptoms of multiple sclerosis include [6]:

• Problems with balance and coordination
• Cognitive problems
• Visual disturbances
• Numbness and tingling sensations, sometimes affecting only one part of the body

MS is estimated to affect 1 million Americans, though it’s more prevalent in people assigned female at birth than people assigned male at birth. [5]

Most people who have MS are diagnosed between 20 and 40 years old. It’s important to receive an MS diagnosis as early as possible, as untreated MS may lead to significant physical limitations like [5]:

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

Although MS is not a curable condition, you can manage it with proper care. Typical treatment plans include both medications and physical therapy. [5]

Diabetic Neuropathy

Nerve damage caused by diabetes is referred to as diabetic neuropathy. Diabetes is associated with chronically high levels of blood glucose, which can result in nerve damage in various areas of the body.

Symptoms of diabetic neuropathy will vary from person to person depending on the type of neuropathy they have. However, numbness and tingling in the limbs are common symptoms.

Diabetic neuropathy affects more than half of all people who have diabetes, but working closely with one’s care team to manage blood sugar levels may help reduce the risk.

Other Possible Causes of Left Arm Tingling or Numbness

If you’re wondering, “why is my left arm tingling?” it’s important to understand that paresthesia isn’t always directly related to nervous system dysfunction or diseases. The following conditions may offer an alternative explanation for why you may experience left arm numbness.

Vitamin B12 Deficiency

Vitamin B12 is a key nutrient that helps the nervous system function well, so it probably doesn’t come as too much of a surprise that a B12 deficiency can lead to paresthesia—a tingling feeling or numbness that typically affects the arms, hands, legs, or feet. [7]

The recommended dietary allowance for vitamin B12 is 2.4 mcg per day for adult men and non-pregnant women.8 Vitamin B12 is found in many animal products including fish, poultry, eggs, meat, and milk—and it’s also available as a nutritional supplement for those who need to boost their intake but don’t get enough of this vitamin from dietary sources.

Inadequate Blood Flow

If you’ve ever fallen asleep in an odd position, you may have woken up to a pins and needles left arm feeling caused by inadequate blood flow.

While it’s highly common during sleep, restricted blood flow to the arms can also result from injuries or underlying health conditions such as:

• High blood pressure
• Diabetes
• Kidney failure

If inadequate blood flow is causing tingling in your left arm, you may also experience pain, swelling, and cold hands and fingers.

Hypothyroidism

An underactive thyroid, a condition also known as hypothyroidism, can cause a number of symptoms, including numbness, tingling, and a painful “pins-and-needles” sensation that can affect the arms. [9]

Hypothyroidism results from the underproduction of thyroid hormone by the thyroid gland, and can also lead to symptoms like [9]:

• Fatigue
• Cold sensitivity
• Weight gain
• Dry skin

Hypothyroidism is not curable, but it can be very responsive to treatment. Most healthcare providers treat the condition with a thyroid medication called levothyroxine. This helps supply your body with thyroid hormones it can’t produce on its own. [9]

Fractures

A bone fracture in your arm can cause inflammation, swelling, and pain, and interfere with nearby nerves, causing numbness and tingling.

Other symptoms of a fracture in the arm include:

• A misshapen arm
• A visibly out-of-place joint
• Bleeding
• A protruding bone
• Limited mobility in the arm
• The inability to move the arm

If you suspect you have a bone fracture, seek medical attention right away.

Stroke

One critical condition associated with tingling in left hand and arm is a stroke. A stroke is a serious and potentially fatal condition associated with sudden numbness in the face, leg, or arm. Strokes often affect just one side of the body. [10]

A stroke occurs when blood flow to a part of the brain is interrupted, resulting in the death of brain cells. [10] A stroke may lead to symptoms in your left arm if the brain cells controlling that arm are affected. [10]

In addition to numbness and tingling, you may also experience [10]:

• Sudden confusion
• Difficulty speaking or understanding speech
• Difficulty seeing (which can affect one or both eyes)
• Difficulty walking (which can include dizziness, lack of balance, and loss of coordination)
• Sudden, severe headache

If you or someone else is having a stroke, call 9-1-1 immediately so EMS responders can start life-saving treatment before arrival at an emergency room.

What To Do If You Experience Numbness or Tingling in the Left Arm

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.

Find More Insights on Your Well-Being at Everlywell

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, 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.

1. Professional CC medical. Paresthesia: When to pin down a cause. Cleveland Clinic. URL. Accessed October 9, 2023.
2. Professional CC medical. Left Arm Numb: What it is, causes, treatments & emergency care. Cleveland Clinic. URL. Accessed October 9, 2023.
3. Herniated disk. Mayo Clinic. February 8, 2022. URL. Accessed October 9, 2023.
4. Cubital Tunnel syndrome. Johns Hopkins Medicine. August 8, 2021. URL. Accessed October 9, 2023.
5. Professional CC medical. Multiple sclerosis (MS): Symptoms, causes, diagnosis & treatments. Cleveland Clinic. URL. Accessed October 9, 2023.
6. Schneik4. 4 early signs of ms you shouldn’t ignore. Cleveland Clinic. March 29, 2022. URL. Accessed October 9, 2023.
7. Professional CC medical. Vitamin B12 deficiency: Symptoms, causes & treatment. Cleveland Clinic. URL. Accessed October 9, 2023.
8. Office of dietary supplements - vitamin B12. NIH Office of Dietary Supplements. URL. Accessed October 9, 2023.
9. Hypothyroidism (underactive thyroid). Mayo Clinic. December 10, 2022. URL. Accessed October 9, 2023.
10. Stroke Signs and Symptoms. Centers for Disease Control and Prevention. URL. Accessed October 9, 2023.