Numbness and tingling are abnormal sensations that can occur anywhere in your body, but are often felt in your fingers, hands, feet, arms, or legs.

There are many possible causes:

• Remaining in the same seated or standing position for a long time
• Injury to a nerve -- for example, a neck injury may cause you to feel numbness anywhere along your arm or hand, while a low back injury can cause numbness or tingling down the back of your leg
• Pressure on the spinal nerves, such as from a herniated disk
• Pressure on peripheral nerves from enlarged blood vessels, tumors, scar tissue, or infection
• Shingles or herpes zoster infection
• Lack of blood supply to an area -- for example, cholesterol (plaque) build up from atherosclerosis in the legs can cause pain, numbness, and tingling while walking (this is called vascular claudication); frostbite can also reduce blood supply and lead to numbness
• Other medical conditions, including:
  • Carpal tunnel syndrome (pressure on a nerve at the wrist)
  • Diabetes
  • Migraines
  • Multiple sclerosis
  • Seizures
  • Stroke
  • Transient ischemic attack (TIA), sometimes called a "mini-stroke"
  • Underactive thyroid
  • Raynaud's phenomenon
• Abnormal levels of calcium, potassium, or sodium in your body
• A lack of vitamin B12 or other vitamin
• Use of certain medications
• Toxic nerve damage due to lead, alcohol, or tobacco
• Radiation therapy

Your doctor should identify and treat the underlying cause of your numbness or tingling. Treatment of the underlying condition may reverse the symptoms or prevent them from becoming worse. For example, if you have carpal tunnel syndrome or low back pain, your doctor may recommend certain exercises.

If you have diabetes, your doctor will discuss ways to control your blood sugars.

Low levels of vitamins will be treated with vitamin supplements.

Medications that cause numbness or tingling may need to be switched or adjusted. You should not change or stop taking any of your medicines or take large doses of any vitamins or supplements until you have talked with you doctor.

Because numbness can cause a decrease in feeling, you may be more likely to accidentally injure a numb hand or foot. Take care to protect the area from cuts, bumps, bruises, burns, or other injury.

Go to a hospital or call your local emergency number (such as 911) if:

• Weakness or paralysis occurs with numbness or tingling
• Numbness or tingling occur just after a head, neck, or back injury
• You cannot control the movement of an arm or a leg or you have lost bladder or bowel control
• You are confused or have lost consciousness, even briefly
• You have slurred speech, change in vision, difficulty walking, or weakness

Call your doctor if:

• Numbness or tingling has no obvious cause (like a hand or foot "falling asleep")
• You have pain in your neck, forearm, or fingers
• You are urinating more often
• Numbness or tingling is in your legs and worsens when you walk
• You have a rash
• You have dizziness, muscle spasm, or other unusual symptoms

Your health care provider will take a medical history and perform a physical examination, with careful evaluation of your nervous system.

Medical history questions may include the following:

• What part or parts of your body have numbness or tingling? The trunk? Your legs or feet? Your arms, hands, or fingers?
• Which side of your body is involved?
• Which aspect of the specific body part? For example, is your inner thigh, calf, or foot affected? Your palm, fingers, thumb, wrist, or forearm?
• Does the numbness or tingling affect your face? Around your eyes? Your cheeks? Around your mouth? Is one or both sides of your face involved?
• Does the part of your body with numbness or tingling change colors? Does it feel cold or warm?
• Do you have other abnormal sensations?
• Do you ignore everything on the affected side?
• How long have you had the numbness or tingling?
• When did it start?
• Does anything make it worse like exercise or standing for long periods of time?
• Do you have any other symptoms?

Your doctor may also ask you questions to determine your risk for stroke, thyroid disease, or diabetes, as well as questions about your work habits and medications.

Blood tests may include:

• Complete blood count ( CBC)
• Electrolyte level (measurement of body chemicals and minerals)
• Thyroid function tests
• Measurement of vitamin levels
• Heavy metal or toxicology screening

Imaging tests may include:

• CT scan of the head
• CT scan of the spine
• MRI of the head
• MRI of the spine
• Angiogram (A test that uses x-rays and a special dye to see inside the blood vessels)
• CT angiogram
• X-ray of the affected area
• Ultrasound of neck vessels to determine your risk for TIA or stroke
• Vascular ultrasound

Other tests that may be done include:

• Electromyography and nerve conduction studies to measure how your muscles respond to nerve stimulation
• Lumbar puncture (spinal tap) to rule out central nervous system disorders
• Cold stimulation test may be done to check for Raynaud's phenomenon

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Piazzini DB, Aprile I, Ferrara PE, et al. A systematic review of conservative treatment of carpal tunnel syndrome. Clin Rehabil. 2007;21(4):299-314.

Rowland LP. Diagnosis of pain and paresthesias. In: Rowland LP, ed. Merritt???s Neurology. 11th ed. Baltimore, Md: Lippincott Williams & Wilkins; 2005:chap 5.