Why Is My Arm Falling Asleep At Night?

If you have ever awakened with a numbness or tingling in your arm or hand, you may immediately wonder how or why it happened. What does it mean for part of the body to “fall asleep?”

It is common to say that a body part has “fallen asleep” when it feels numb or prickles with "pins and needles." The medical term for this sensation is paresthesia. There may be pain or other discomfort associated with paresthesia, especially as it wears off.

This article explains the possible reasons why your arm might fall asleep at night. It explains how the position you sleep in might cause paraesthesia, and when to see a healthcare provider.

What Causes This Sensation?

Paraesthesia is a symptom, not a medical condition of its own. It can be a temporary symptom, like when your arm "falls asleep." Or, it can be a chronic (long-term) symptom of an underlying medication condition.

Many people believe that paraesthesia occurs due to loss of blood flow, but that's not the case. Paraesthesia is a nervous system problem. It happens when a nerve in your arm, leg, or another extremity gets compressed.

Nerves carry sensory information from your body to your brain. They allow you to perceive pain, temperature, pressure, and other sensations. They enable voluntary movements, reflexes, and much more.

If a nerve gets compressed or damaged, you will experience a loss of sensation, an inability to move any muscles controlled by the affected nerve, and possibly other symptoms like tingling.

This is essentially what happens when you experience paraesthesia or your arm falls asleep. There are several conditions or situations that can cause it:

Sleeping Position

There's not much you can do to control your body position while sleeping.

Without realizing it, your sleeping position may put pressure on nerves in your arm, especially if you sleep with it bent at an odd angle or tucked under your head or body.

The radial nerve, which runs from your armpit to your hand, is commonly affected by nerve compression during sleep. The numbness and tingling this causes usually goes unnoticed as sleep resumes. Most people only notice it if they wake up while it is happening.

Certain sleep positions may be more likely to cause nerve compression than others, such as:

• Sleeping with wrists curled inward
• Hands under your body or head
• Head on your forearm
• Arm tucked under your torso
• Head on a pillow that causes spinal misalignment

Peripheral Neuropathy

"Neuropathy" is the general medical term for nerve damage. Peripheral neuropathy refers to any nerve damage that affects the peripheral nervous system. The nerves in your arms, legs, and anywhere else outside of your brain and spinal cord are peripheral nerves.

Peripheral neuropathy is common. It may be triggered by diabetes, hypothyroidism, vitamin B12 deficiency, chronic kidney disease, or exposure to heavy metals. Over time, the nerves may gradually become damaged, and this injury may be irreversible.

Someone with peripheral neuropathy may experience one or more of the following:

• Muscle weakness
• Cramps
• Muscle twitching
• Numbness
• Loss of sensation in the affected area
• Loss of balance or other functions in the affected area
• Emotional disturbances
• Sleep problems
• Inability to feel pain in the affected area

There are over 100 types of peripheral neuropathy, including diabetic neuropathy, chemotherapy-induced neuropathy, and alcoholic neuropathy. The exact symptoms one experiences, along with how severe those symptoms are, depends on the type of neuropathy they have.

Vitamin B12 Deficiency

Another common cause of peripheral neuropathy is vitamin B12 deficiency. This deficiency is typically detected in people ages 40 years and above. In many cases, they present to healthcare providers complaining of neurological (nerve-related), behavioral, or cognitive symptoms.

Vitamin B12 plays a critical role in several body processes. The vitamin maintains the health of nerves, along with the protective covering around nerves, known as the myelin sheath.

Peripheral neuropathy related to vitamin B12 deficiency may result in:

• Pain
• Numbness
• Tingling
• Loss of sensation
• Movement problems
• Decreased muscle mass

A person with vitamin B12 deficiency may also experience psychiatric disturbances, such as depression, delusions, and cognitive changes.

Carpal Tunnel Syndrome

The carpal tunnel is a passageway in the wrist through which passes the median nerve. If the median nerve gets compressed in this tunnel, carpal tunnel syndrome can ensue.

Carpal tunnel syndrome is also a type of peripheral neuropathy. With this syndrome, you may experience the following symptoms in one or both hands:

• Weakness when gripping objects
• Pain
• Numbness
• Burning or tingling
• Swelling in fingers
• Inability to use the hands, wrist, or fingers

Many people with carpal tunnel syndrome experience pain and numbness in their wrists or hands that is particularly worse at night and may even interrupt sleep.

Carpal tunnel syndrome is often caused by repetitive movements, such as typing or sewing. Your risk of developing carpal tunnel syndrome is also higher if you have rheumatoid arthritis, a previous wrist injury, or were born with a more narrow carpal tunnel.

Genetic Disorders

Certain genetic disorders can predispose affected individuals to nerve injuries. One such disorder is known as hereditary neuropathy with a predisposition to pressure palsies (HNPP).

HNPP leads to episodes of weakness and loss of sensation often associated with compression of single nerves. It most commonly affects nerves in the wrists, elbows, and knees, but may also affect nerves in the fingers, shoulders, feet, and scalp.

Depending on the body areas affected, a person with HNPP may experience:

• Tinging, prickling, or numbness in affected limbs
• Voice abnormalities
• Inability to move vocal cords
• Slowed reflexes
• High-arched feet
• Breathing problems

HNPP symptoms usually begin during adolescence or early adulthood, but can start at any time.

Stroke

A stroke can cause symptoms that feel similar to your arm falling asleep, and may include:

• Paralysis or weakness in one or more arm muscles
• Tightness in one or more arm muscles
• Increase or decrease in arm muscle tone
• Numbness or loss of sensation in the arm

Stroke occurs when a blood vessel to the brain gets blocked (ischemic stroke), or there is bleeding in the brain (hemorrhagic stroke). The symptoms you experience depend on the location of the stroke.

Other possible symptoms of stroke include:

• Confusion, trouble speaking, or trouble understanding speech
• Numbness or weakness, usually on one side of the body
• Sudden, severe headache
• Trouble seeing from one or both eyes
• Trouble walking, dizziness, or loss of balance

How Is Paresthesia Prevented?

There are steps you can take to prevent your arm from falling asleep at night:

• Use a supportive mattress: If your mattress is too soft, sloped, or uneven, you may be more likely to wedge your arm beneath your head or body. If possible, opt for firmer pillows and a mattress that supports your whole body.
• Try a wrist brace: See if wearing a firm wrist brace helps by preventing your wrist from bending beneath your head. If you have carpal tunnel syndrome, specific carpal tunnel wrist braces are ideal.
• Get your blood pressure checked: High blood pressure is a risk factor for stroke, diabetes, and neuropathy. People ages 18 to 39 who do not have a history of high blood pressure should get theirs checked every three years at minimum. People ages 40 and up should get theirs checked at least once per year.
• Avoid excessive alcohol intake: Drinking too much alcohol can cause you to fall asleep in an awkward position and potentially place too much pressure on your arm.

You may not be able to prevent paresthesia in every case. Since paresthesia can be a symptom of stroke, diabetes, and other health problems, it's important to get regular medical screenings with a healthcare provider.

When Should I Worry?

Most people experience their arm falling asleep on occasion. When it's an occasional occurrence that resolves after you adjust your position, it's nothing to worry about.

However, paresthesia becomes more concerning when it:

• Doesn't resolve after adjusting your position
• Spreads to other parts of the body or travels from your neck or shoulder to your arm
• Is accompanied by other new or concerning symptoms, such as a severe headache, trouble speaking, or vision problems
• Happens suddenly and is not due to your sleeping position

If you have a history of cardiovascular disease or diabetes and are experiencing paresthesia more frequently, this may be a sign of a worsening problem.

When to See a Healthcare Provider

When your arm falls asleep due to nerve compression, it should resolve soon after you adjust your body position. If it doesn't go away or seems to be getting worse, you may need medical attention.

Give your healthcare provider a call if:

• You experience frequent paresthesia in your arm
• Your symptoms are interfering with your sleep
• You have diabetes or cardiovascular disease and are experiencing paresthesia increasingly

If you develop paresthesia suddenly or have any other sudden, concerning symptoms, call 911 immediately.

Do not hesitate to get medical attention if you feel worried about the sensation—or loss of sensation—in your arm or elsewhere in your body.

Summary

The sensation of your arm falling asleep at night is called paresthesia. Paresthesia occurs when nerves get compressed, leading to tingling, numbness, or loss of function. This is usually temporary and resolves within minutes of adjusting your body position. You may be able to prevent it by using a more supportive pillow or wearing a wrist brace to bed.

Some conditions, like carpal tunnel syndrome, diabetes, and hypothyroidism can cause nerve damage (neuropathy). These conditions may also result in weakness, numbness, or loss of sensation in your arms or elsewhere. If you experience paresthesia in addition to sudden symptoms like headache, vision problems, or confusion, call 911 right away.