Why Is My Arm Asleep? 6 Reasons Your Limbs Go Numb When You're Sleeping

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Waking up with a tingling or numbness in your arm can be a little alarming, especially if you haven't noticed it before. While it can be caused by underlying health conditions, it may be nothing more than your sleeping position. Being aware of the different reasons behind why your arms go numb while sleeping can help you determine if it's harmless or something you should be talk to your doctor about.

"There may be an assortment of reasons why an arm may go numb during sleep, some benign, while others are more concerning," Keiland Cooper, neuroscientist at the University of California Irvine, tells Bustle. "The general case of this is called paresthesia, more commonly referred to and experienced by the 'pins and needle' in a hand, foot, arm, or leg."

This is what usually happens when there's prolonged pressure on a nerve. When you're sleeping, the way your body is positioned can inhibit yours nerves from doing what they're supposed to do, which is to send signals throughout your body. When it's not working right, it can lead to numbness.

While it's usually harmless, chronic paresthesia may indicate a bigger problem. "In any case, it never hurts to bring it up to your doctor so they can take your specific circumstances into consideration," Cooper says.

So here are some surprising reasons why your arms go numb while sleeping, according to experts.

1. A Vitamin B12 Deficiency

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Vitamin B12 is important because it helps to keep the body's nerve and blood cells stay healthy. According to Dr. Adarsh Vijay Mudgil, M.D., owner of Mudgil Dermatology in New York, a vitamin B12 deficiency can cause neurological issues like numbness. It can also lead to tingling in the hands, legs, and feet, tiredness, weakness, difficulty walking, and anemia. You can easily get more vitamin B12 in your system by consuming meat, eggs, poultry and dairy. Strict vegetarians and vegans are at a higher risk for developing a deficiency, so taking a supplement or eating grains fortified with the vitamin could be beneficial for them.

2. Diabetes

“It's not uncommon for one's arm to go numb while sleeping," Mudgil says. "In very rare cases, however, this could represent an underlying health condition like diabetes." According to the Mayo Clinic, this is called diabetic neuropathy. When your blood sugar levels are high, it can be toxic to the nerves and cause some damage. It's common in people with diabetes, but if not taken care of it can cause serious complications. Many times, symptoms develop gradually so many people won't even realize anything is wrong until they start feeling really off. There are also four types of diabetic neuropathy. Peripheral neuropathy is the most common and usually causes the numbness, tingling, and sharp pains felt in the arms, legs, and feet.

3. Multiple Sclerosis

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Multiple sclerosis is another health condition that can cause numbness in the arms. In fact, numbeness in the limbs is one of the most common symptoms of MS. According to the National Multiple Sclerosis Society, numbness in the arms, face, and body, is one of the first symptoms people start to notice. More often than not, this symptom is bothersome but harmless. Because of that, doctors don't usually prescribe any medication unless it becomes more severe and painful.

4. Sleeping On Your Side

How you sleep really matters. If you're a side-sleeper, you've probably woken up to numb arms at some point in your life. "Awakening with numb arms is typically due to a temporary compression injury to a nerve," Dr. Anil Rama, MD, sleep doctor and adjunct clinical faculty at the Stanford Center for Sleep Sciences and Medicine, tells Bustle. "Side-sleepers are more prone to place pressure on one or more nerves in the arm they're sleeping on." Once you wake up and change positions, the pressure on the nerve is released and the sensation in your arm should return. According to Dr. Rama, it's an "annoying phenomenon," but usually not something to be overly concerned about.

5. Sleeping With Your Neck In A Weird Position

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"If your entire arm is numb that means you either slept on your shoulder the wrong way or slept with your neck in a funny position, affecting the nerves coming directly from the spine," Anthony Kouri, MD, orthopedic surgeon at the University of Toledo Medical Center who treats patients with sleep related issues, tells Bustle. If your arm numbness is related to your neck, stretching your neck out or moving it in a certain way can help to alleviate the numbness and tingling. "If you notice that raising your arm above your head improves your numbness and tingling, that is a tell-tale sign that you have a pinched nerve in your neck," he says.

6. Carpal Tunnel Syndrome

Carpal tunnel syndrome is a condition that can cause numbness and tingling in the hands and arms. According to the Mayo Clinic, it's typically caused by a compressed nerve that runs through the wrist. There are several different things that can cause carpal tunnel such as repetitive use of the same hand and wrist movements, injury, genetics, and the positioning of your hand and wrist. A 2011 study published in the journal Hand found a link between sleeping on the side and carpal tunnel syndrome.

Your arms going numb while sleeping is pretty normal, especially if you sleep in a certain position. If you experience numbness that's not related to the way you're sleeping, it's not a bad idea to talk to your doctor.