That strange tingling or numbness you sometimes feel in your hands, often described as “pins and needles,” is a common phenomenon known medically as paresthesia. It can occur in many parts of the body, but hands are a frequent site — especially during sleep.

Most people experience this sensation occasionally, and it’s typically nothing to worry about. The most common cause is simply an awkward sleeping position that compresses the nerves or restricts blood flow to your hands or arms. Once you shift positions and relieve the pressure, the sensation usually fades quickly.

However, if the tingling or numbness happens often, lasts longer than a few minutes, or occurs during the day as well, it could be a sign of an underlying issue. One possible cause is carpal tunnel syndrome, which involves pressure on the median nerve in the wrist. This condition is especially common among people who perform repetitive hand movements, such as typing or working with tools.

Another cause could be cervical radiculopathy, where a nerve in your neck becomes irritated or compressed — often from a herniated disc or arthritis. This can cause numbness or tingling in the hands, arms, or fingers, and may require imaging tests to diagnose.

Diabetes is another important condition to consider. Diabetic neuropathy, a form of nerve damage caused by high blood sugar levels, can produce numbness or tingling in the extremities. This is a more gradual and chronic condition, unlike the temporary effects of poor posture during sleep.

Occasionally, vitamin deficiencies — especially low levels of B12 — can lead to paresthesia. Since vitamin B12 plays a key role in nerve health, a deficiency can lead to numbness, weakness, and balance issues if left untreated.

Other less common but serious causes include multiple sclerosis, stroke, or tumors pressing on nerves. These are typically accompanied by other symptoms and require prompt medical attention.

In most cases, though, numb hands during sleep are harmless. But if the tingling is frequent, worsening, or accompanied by other symptoms, it’s wise to consult a healthcare provider for a proper diagnosis and treatment plan.