By Korin Miller– Self
It happens to everyone: You sit in one position for a while and suddenly your leg, foot, arm, or even butt falls asleep. You’ve probably dealt with this your whole life and still don’t understand why your foot can feel fine one moment and then the next as if it’s being stabbed with tiny needles.
Turns out, there’s a medical name for this—paresthesia—and it describes that burning or prickling sensation that you feel after you sit with your legs crossed too long, or you fall asleep in a weird position. You may have heard that it has something to do with blood flow, but it actually happens when there’s sustained pressure put on a nerve, according to the National Institute of Neurological Disorders and Stroke.
There are a few different causes for paresthesia.
Usually, you get that pins and needles feeling because some of your nerves are being compressed, Ilan Danan, M.D., M.Sc., a sports neurologist at Kerlan-Jobe Center for Sports Neurology and Pain Medicine at Kerlan-Jobe Orthopaedic Clinic in Los Angeles, tells SELF. This can happen when you sit a certain way or stay in a position for a long time. “As soon as you relieve that pressure with movement, the nerve starts to breathe again and you no longer have that feeling,” he says. That’s known as temporary paresthesia, and it’s pretty harmless, Dr. Danan says.
But it’s also possible to lose feeling in your legs, feet, etc. as part of a medical condition like diabetes, thyroid disease, bone marrow problems, or a lack of vitamin B12, Amit Sachdev, M.D., an assistant professor and director of the division of neuromuscular medicine at Michigan State University, tells SELF. This is different from what you experience when you’re an otherwise healthy person—it can come on without sitting in an unusual position and can last longer than temporary paresthesia. And people can suffer what’s known as chronic paresthesia if they have an underlying neurological disease like multiple sclerosis or traumatic nerve damage, per the National Institute of Neurological Disorders and Stroke.
While it’s usually no biggie if a part of your body falls asleep, it’s important to keep some things in mind.
First, it’s probably just because you sat in a weird way and if you get up and move around it should make everything feel OK pretty quickly, Dr. Danan says. But if you change positions and that doesn’t help, or you weren’t sitting or resting in a way that would compress your nerves in the first place, it’s important to take stock of the situation.
If half of your body suddenly goes numb and you have coordination problems, this is a brain problem, Dr. Sachdev says, and could be a sign of a stroke. In this case, call 911 immediately. If it’s a smaller area of your body, such as if your thumb and two nearby fingers go numb, it’s more likely that you have a pinched nerve, he says—but it’s still a good idea to get it checked out by your doctor if the feeling persists.
It’s also important to see a doctor if you find that you have that pins and needles feeling often, or you notice that you have it sooner than you have in the past, Dr. Danan says. For example, maybe you used to get it after crossing your legs for 10 minutes, and now it occurs after two minutes. “If that’s happening to you, you need to get it evaluated,” he says—it could be a sign of an underlying medical condition like diabetes or multiple sclerosis. Weakness and muscle coordination issues that come with that pins and needles feeling should also be checked out, Dr. Sachdev says.
Again, it’s usually just a nerve compression issue if one of your body parts falls asleep or gives you pins and needles, but if you keep having that issue or the feeling doesn’t go away when you get up and move around, you should visit your doctor. Even then it’s pretty likely that it’s a pinched nerve, but it’s a good idea to have it evaluated.
Just don’t panic if you wake up in the morning and your arm feels like it weighs 500 pounds after you slept on it—that’s no big deal. “This is relatively benign and more common than you’d think,” Dr. Danan says.