Numbness in fingers and toes and when tests are needed

Symptoms of numbness in the fingers and toes range from a subtle tingling and cold sensation to a severe burning sensation, loss of sensation, or a feeling that the fingers are «not yours.» In the vast majority of cases, this is simply the result of prolonged compression of the nerve endings – for example, during sleep or sedentary work.

However, regular or progressive numbness is a reason to be wary. It can be caused by various pathologies: hypovitaminosis (especially B12), anemic conditions, thyroid dysfunction, diabetic neuropathy, the consequences of injuries or systemic inflammatory reactions. The Mayo Clinic medical community emphasizes that peripheral neuropathy occurs under the influence of many factors - from genetic predisposition and infections to toxic damage and autoimmune processes, with diabetes remaining one of the most common causes.

It makes no sense to take tests after a random episode of numbness. However, when numbness is combined with pain, muscle spasms, rapid fatigue, or gait instability, laboratory examination becomes a key stage of diagnosis, as it allows you to detect what remains hidden during a standard examination.

When finger numbness may be temporary

Sometimes numbness occurs due to a simple mechanical cause. For example, a person has been sitting with their legs crossed for a long time, sleeping on their arm, holding their phone in one position, or working on a computer without interruption. In such cases, the unpleasant sensation usually goes away after a change in position, light movement, or rest.

Temporary numbness is usually not a cause for concern if:

• it appeared after an awkward posture;
• passed quickly after the movement;
• does not repeat daily;
• not accompanied by weakness;
• no pain, burning, or loss of coordination;
• the symptom does not spread to the entire arm or leg.

But if a person notices that their toes are numb for no apparent reason, that's a different story. Symmetrical numbness of the feet, gradual spread from the toes to the shins, burning at night, or decreased sensitivity that makes it difficult to feel temperature, pain, or touch, is especially worrisome.

When to see a doctor quickly

There are situations when numbness cannot be waited out or observed at home. If it begins suddenly, affects one side of the body, is accompanied by weakness, slurred speech, dizziness, confusion, or a severe headache, it may be a sign of an emergency.

The CDC lists signs of a stroke as sudden numbness or weakness in the face, arm, or leg, especially on one side of the body, as well as sudden confusion, trouble speaking, vision problems, balance problems, or severe headache. The Mayo Clinic also recommends seeking emergency care immediately if the numbness begins suddenly, occurs after a head injury, involves the entire arm or leg, or is accompanied by weakness, paralysis, slurred speech, dizziness, or a severe headache.

Don't delay seeking help if you have it.

• sudden numbness of the face, arm, or leg;
• numbness on only one side of the body;
• weakness in an arm or leg;
• speech disorders;
• facial asymmetry;
• severe dizziness;
• loss of balance;
• severe headache without an obvious cause;
• numbness after a head, neck, or back injury.

In such cases, tests are not the first step. An urgent medical evaluation is required first.

Why fingers can go numb with vitamin B12 deficiency

Vitamin B12 is needed for normal nervous system function and the production of red blood cells. When it is deficient, a person may experience weakness, fatigue, dizziness, impaired sensation, tingling or numbness in the hands and feet. MedlinePlus notes that low levels of B12 can cause numbness or tingling in the hands and feet, weakness, and loss of balance.

B12 deficiency can occur due to insufficient intake from food, malabsorption, gastrointestinal diseases, after certain surgeries, with long-term use of certain medications, or in people who do not consume animal products.

If finger numbness is accompanied by fatigue, paleness, shortness of breath on exertion, unsteadiness in gait, or memory impairment, your doctor may recommend checking: vitamin B12 level. Such analysis helps to understand whether a symptom may be related to a deficiency that affects the nervous system.

Diabetes and numbness in toes

Numbness, burning, or tingling in your feet can be a sign of nerve damage from long-term high blood sugar levels. The CDC explains that high blood sugar can lead to nerve damage, called diabetic neuropathy, which can affect your feet, legs, hands, and arms.

With diabetic neuropathy, symptoms often begin in the feet. A person may experience numbness in their toes, burning, tingling, pain, decreased sensation, or discomfort at night. Sometimes, on the contrary, there are almost no symptoms, but sensitivity is reduced, so a person feels rubbing, trauma, cold or heat worse.

If numbness in your toes recurs, especially if you have thirst, frequent urination, weight gain or loss, fatigue, or a family history of diabetes, your doctor may prescribe: blood glucose test and other studies of carbohydrate metabolism.

What tests may be needed for numbness in the fingers?

There is no one-size-fits-all test for finger numbness. Your doctor will select the test based on your symptoms, age, underlying medical conditions, medications, diet, lifestyle, and physical exam findings. The Mayo Clinic notes that if peripheral neuropathy is suspected, blood tests can help detect low vitamin levels, diabetes, signs of inflammation, or metabolic disorders that can cause nerve damage.

The table is not a substitute for medical advice. It shows which areas of investigation may be appropriate when numbness recurs or has an unexplained cause.

When tests are especially appropriate

Laboratory tests should be discussed with your doctor if numbness is not a one-time episode after awkward posture. This is especially true if symptoms recur, worsen, or are combined with other changes in well-being.

Tests may be needed if there is

• numbness of the fingers daily or several times a week;
• burning sensation in the feet;
• tingling in the hands and feet;
• decreased sensitivity to cold, heat, or pain;
• muscle weakness;
• cramps;
• unsteadiness of gait;
• prolonged fatigue;
• pallor;
• weight loss for no apparent reason;
• thirst and frequent urination;
• hair loss;
• memory or concentration impairment;
• symptoms after an infection;
• numbness due to chronic diseases.

If numbness occurs after starting a new medication, chemotherapy, or taking a long-term medication, you should also tell your doctor. The NINDS notes that nerve damage can be caused not only by diabetes and deficiencies, but also by toxins, alcohol, certain medications, autoimmune processes, and other factors.

Numbness in the hands and possible local causes

When numbness occurs mainly in the fingers, the cause is not always related to blood tests. Sometimes the problem can be local: nerve compression in the wrist, neck or elbow, prolonged computer work, monotonous movements, injury or overexertion.

For example, when a nerve is compressed, individual fingers may go numb, rather than the entire hand. The symptom may worsen at night, while working with a mouse, telephone, steering wheel, or after straining the hand. In such cases, the doctor may prescribe not only tests, but also a neurological examination, electroneuromyography, or imaging methods.

But if hand numbness is combined with fatigue, anemia, tingling in the feet, weakness, or other systemic manifestations, laboratory testing becomes more appropriate.

Numbness in the legs and why you shouldn't ignore it

Numbness in the toes is often taken less seriously than numbness in the hands because it doesn't always cause immediate discomfort. But the feet can be the first to respond to sensory loss related to diabetes or peripheral neuropathy.

The CDC notes that nerves in the feet and legs are often affected in diabetes, and people with nerve damage may have numbness, tingling, or pain, and sometimes experience no symptoms at all.

If a person has poor toe sensation, they may not notice abrasions, calluses, cracks, or minor injuries. This is especially dangerous in diabetes, where healing can be slower. Therefore, it is better not to ignore recurring numbness in the feet.

Can stress cause numbness in fingers?

Stress and anxiety can be accompanied by tingling, coldness in the extremities, muscle tension, shallow breathing, or tremors. But you should only attribute numbness to nerves after your doctor has ruled out common physical causes.

If a person has chronic stress, but along with it there is fatigue, weakness, sleep disturbances, palpitations, weight loss, thirst, diarrhea, or anemia, tests can help not to miss a condition that requires treatment.

Anxiety numbness often comes in waves and can be accompanied by a rapid heartbeat, shortness of breath, or tension. But even in this situation, you should not self-diagnose without consulting a doctor.

What results cannot be interpreted independently

Patients often try to find an explanation in one indicator. For example, they saw a low ferritin and decided that it caused the numbness. Or they found a slightly elevated glucose and immediately thought of diabetic neuropathy. In fact, the doctor does not evaluate a single number, but the whole picture.

Do not interpret it yourself.

• low or borderline B12;
• elevated glucose;
• altered glycated hemoglobin;
• low ferritin;
• anemia;
• elevated TSH;
• elevated C-reactive protein;
• changes in liver or kidney function.

The same numbness in different people can have different causes. Therefore, tests should not just be "passed", but correctly matched with symptoms.

How to prepare for tests

Preparation depends on the specific test. For some blood tests, your doctor or laboratory may recommend that you give your blood on an empty stomach, especially if they are testing glucose, biochemical parameters, or certain metabolic parameters.

Before taking the tests, it is advisable to clarify

• Do I need to come on an empty stomach?;
• is it possible to drink water;
• Is it necessary to temporarily coordinate medication intake?;
• do vitamin supplements affect the result;
• whether you need to report taking B12, folic acid or iron supplements;
• Is it worth taking the tests in the morning?;
• Which tests are better to take in one day?.

If a person is already taking vitamins or iron supplements, they should not be discontinued before the test. It is better to clarify this with a doctor, as different tests have different requirements.

FAQ

Can numbness in fingers be due to a lack of vitamins?

Yes, it can. Most often, in the context of numbness and tingling, doctors pay attention to vitamin B12, because its deficiency can affect the nervous system. But the symptom cannot be explained only by vitamins without an examination and tests.

Do I need to take tests if my fingers only go numb at night?

This numbness may be related to the position of the hand or nerve compression, but if it recurs frequently, wakes you up at night, or is accompanied by pain, weakness, or tingling in the feet, you should see a doctor.

What is the first test for numbness in the fingers?

There is no one test that fits all. Often, the doctor will start with a complete blood count, glucose, glycated hemoglobin, vitamin B12, ferritin, TSH, and biochemical parameters. The list depends on the symptoms.

Can diabetes start with numbness in the legs?

Yes, in some people, impaired sensitivity in the feet may be associated with diabetic neuropathy. But tests are needed to assess glucose, glycated hemoglobin and doctor's consultation.

When finger numbness is dangerous

Sudden numbness on one side of the body, weakness, speech impairment, facial asymmetry, severe headache, dizziness, or numbness after an injury are dangerous. In such cases, you should seek emergency care.

Numbness in the fingers and toes is sometimes limited to a one-time attack due to an awkward body position. However, in other cases, it can indicate deeper problems: vitamin B12 deficiency, fluctuations in blood sugar, anemia, thyroid dysfunction, or damage to nerve fibers. When this manifestation becomes regular, increases in intensity, or is accompanied by other changes in well-being, laboratory tests allow, instead of guessing, to accurately determine the root cause and build a clear strategy for further actions.

Author: Ulyana Anatolyivna Dzyuba

Director of Medi Lab Plus LLC, a doctor of the highest category. Has over 45 years of practical experience in medicine and laboratory diagnostics. Founder and head of the laboratory since 2007. More details…