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A sleeping hand after a night with a bent wrist is usually harmless. But when tingling and numbness recur, spread, wake you up at night or feel like small electric shocks, it's easy to wonder if it's a pinched nerve, a vitamin deficiency or something else. These types of symptoms are common in healthcare - and the causes range from temporary pressure to diseases that affect nerve function.
What are the most common causes of tingling and numbness?
Tingling, numbness and a rushing electrical sensation are often called paresthesias. This means that the nervous system sends incorrect or disturbed signals, even though the skin is not exposed to any clear stimuli. The problems can come from an individual nerve, from a nerve root in the spine or from more widespread effects on peripheral nerves in, for example, the feet and hands.
You often get important clues based on how the symptoms are located. A hand that goes numb when you cycle or sleep may indicate pressure on a local nerve. Symmetrical tingling in both feet that slowly creeps upwards fits better with polyneuropathy, i.e. a more general nerve involvement.
1. When a nerve is pinched
A very common cause is that a nerve is exposed to pressure. This can happen temporarily, such as when you sit with your legs crossed for too long, but also more permanently in narrow anatomical passages. This often results in numbness, tingling or stabbing pain in a clearly defined area.
The best-known example is carpal tunnel syndrome, where the median nerve is pinched at the wrist. Typical symptoms are numbness and tingling in the thumb, index finger, middle finger and half of the ring finger, often at night or during repetitive hand movements. Many people describe having to shake their hands to regain sensation. Nerves can also be affected higher up. In cervical radiculopathy, i.e. nerve root irritation in the neck, pain can radiate from the neck to the shoulder, arm and hand along with tingling or decreased sensation.
2. Diabetes and other polyneuropathy
When tingling begins in the toes and then gradually becomes more widespread, doctors often think of peripheral neuropathy. It is a collective name for conditions in which peripheral nerves are damaged. Diabetes is the most common cause, and nerve damage can cause tingling, burning, numbness, burning pain and sometimes even poor balance.
The classic pattern is the so-called “stocking and glove distribution”. This means that the symptoms are first noticeable in the farthest parts of the feet, later in the lower legs and sometimes also in the hands. Some people mainly feel numbness, others describe electric shocks, tenderness of the blanket against the skin or that they do not notice small wounds on the feet.
However, polyneuropathy can have more causes than diabetes and can be due to excessive alcohol consumption, kidney or liver disease, certain infections, autoimmune diseases, toxins and certain medications – including chemotherapy – which can damage the nerves themselves. Sometimes no definite explanation is found despite investigation.
3. Vitamin deficiency, especially B12, can cause nerve symptoms
Vitamin deficiency is a treatable cause that is easily missed, especially when the symptoms come on insidiously. Deficiency of vitamin B12 can affect the nervous system and cause tingling, numbness, unsteadiness, balance problems and sometimes cognitive symptoms such as difficulty concentrating. You don't always need to have a clear anemia for nerve symptoms to be present.
A deficiency in B12 can be due to getting too little of the vitamin, but more often it is due to poor absorption. This can be seen in certain gastrointestinal diseases, after surgery in the stomach or intestines, in autoimmune effects on absorption and in connection with certain medications. Nitrous oxide can also contribute to functional B12 deficiency and neurological symptoms.
Other vitamin deficiencies can also play a role, especially in the case of long-term high alcohol consumption or malnutrition. Therefore, blood tests are usually an important part of the investigation when the symptoms do not have an obvious mechanical explanation. Clinical practice often includes checking blood sugar, HbA1c, vitamin B12 and sometimes also folate, thyroid test, blood status and kidney- and electrolyte status depending on the symptom picture.
4. Electric shocks from the back, neck or hyperventilation
Many patients describe sudden, sharp and difficult-to-interpret nerve signals as “electric shocks”. If the shocks go from the back or neck into the arm or leg, it often indicates irritation of a nerve root or other nerve damage along its path. Disc impact, wear and tear changes or narrow passages can contribute.
But sometimes the explanation is less dramatic. Recurrent tingling in the hands, feet or around the mouth can occur during hyperventilation, for example in connection with severe stress or anxiety. This temporarily changes the acidity of the blood, which can cause tingling and a feeling that the body is “crackling”. This does not mean that the symptoms are imaginary – but it does mean that the nervous system is reacting functionally rather than that a nerve is necessarily damaged.
There are also more unusual neurological causes, such as disease of the spinal cord or brain. That is why one always looks at the whole picture: how quickly the symptoms came on, whether they are one-sided or two-sided, whether the force is affected and whether the bladder, bowel, walking or speech have changed at the same time.
When tingling and numbness require rapid assessment
Most tingling is not dangerous, but certain patterns are warning signs. Sudden numbness or weakness in the face, arm or leg – especially on one side – may be stroke or TIA and requires immediate medical attention. Stroke can also cause speech difficulties, vision problems, dizziness or balance problems.
Emergency medical attention should be sought if the numbness comes on quickly and is accompanied by increasing weakness, if the loss of sensation spreads upwards in the body or if you experience numbness in the lower abdomen or lose control of urine or stool. Numbness on both sides below a clear level on the trunk may indicate an impact on the spinal cord. This is a condition that needs to be assessed urgently.
Less urgent, but still important reasons to book a medical assessment are recurrent nocturnal numbness in the hands, new symmetrical tingling in the feet, loss of sensation that does not go away, balance problems or simultaneous unexplained fatigue, weight loss or pain. Then there is often reason to investigate both nerve function and possible underlying causes with blood tests and sometimes neurophysiological tests.
Keep a diary for recurring symptoms
Recognizing the pattern in your symptoms can make a big difference. Feel free to write down when the symptoms occur, where they are located, whether they are awakened by strain, night position or stress, and if you also notice weakness, pain or balance problems. This information helps healthcare providers to more quickly distinguish between a pinched nerve, metabolic problems and more general nerve disease.
