Blood tests ordered for numbness and tingling
| Test | What it checks for |
|---|---|
| Vitamin B12 | Deficiency causes peripheral neuropathy — tingling in both feet then hands |
| Fasting glucose / HbA1c | Diabetic peripheral neuropathy — most common neuropathy cause worldwide |
| TSH | Hypothyroidism causes carpal tunnel syndrome and generalised neuropathy |
| Folate (B9) | Deficiency causes similar neuropathy to B12 |
| Calcium | Low calcium causes tetany — muscle cramps and perioral tingling |
| Vitamin D | Severe deficiency can contribute to neuropathy |
| CBC | Anaemia, especially megaloblastic from B12/folate deficiency |
| ANA / ANCA | Autoimmune neuropathy (lupus, vasculitis) |
| Serum protein electrophoresis | Paraprotein (myeloma) causing neuropathy |
Common causes of numbness and tingling
Diabetic peripheral neuropathy
The most common cause of chronic peripheral neuropathy worldwide. High blood sugar over years damages small nerve fibres, typically causing a 'glove and stocking' distribution of numbness, tingling and burning pain — starting in the feet and moving upward. HbA1c and fasting glucose are diagnostic. Prevention is through excellent glucose control; once established, neuropathy is managed with pain medications (duloxetine, pregabalin, gabapentin).
Vitamin B12 deficiency neuropathy
B12 deficiency causes demyelination of peripheral nerves and the spinal cord (subacute combined degeneration). Numbness starts in both feet and ascends symmetrically, often with loss of vibration and position sense. May coexist with megaloblastic anaemia or occur without anaemia. Serum B12 below 200 pg/mL is diagnostic. Injectable B12 is often used to bypass absorption problems.
Carpal tunnel syndrome
Compression of the median nerve in the wrist causes numbness and tingling in the thumb, index, middle and part of the ring finger — often worse at night and when driving. Very common in hypothyroidism, pregnancy, diabetes and repetitive hand use. TSH should be checked. Confirmed with nerve conduction studies. Treated with wrist splints and sometimes steroid injection or surgery.
Cervical or lumbar radiculopathy
A prolapsed or degenerated disc in the neck or back can compress a nerve root, causing numbness radiating down one arm or leg (dermatomal distribution). Usually one-sided. Blood tests normal. MRI of the spine is diagnostic.
Multiple sclerosis
MS causes demyelination in the central nervous system, producing numbness/tingling in variable distributions, visual disturbance, weakness and bladder problems. Typically affects people aged 20–50 and is more common in women. MRI brain and spine, CSF analysis and evoked potentials are the key investigations. Blood tests are used to exclude other causes.
Questions to ask your doctor
- Is my B12 level low?
- Do I have diabetes or pre-diabetes?
- Should I check my thyroid?
- Do I need nerve conduction studies (NCS)?
- Should I see a neurologist?