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Vitamin D, B12 and Iron Deficiency Tests: Who Should Be Tested and What Results Mean
Fatigue, forgetfulness, numbness and hair loss can be caused by vitamin and mineral deficiencies. Vitamin D, B12 and ferritin tests and how to interpret them.
Contents
Constant tiredness, numb hands and feet, forgetfulness, hair loss or muscle aches often have vitamin and mineral deficiencies behind them. Older people, vegetarians, those who had stomach surgery and people on certain long-term medicines are at higher risk.
Vitamin D
Important for bones, muscles and immunity; mostly made in the skin from sunlight, so deficiency is common in older people who rarely go outside.
Signs: bone and muscle pain, weakness, fatigue, more falls, higher osteoporosis risk.
| 25(OH)D level (ng/mL) | General interpretation* |
|---|---|
| Below 20 | Deficiency |
| 20–29 | Insufficiency |
| 30+ | Generally adequate |
| Above 100 | Risk of excess |
*Thresholds vary slightly between guidelines.
Vitamin B12
Needed for nerves and blood production; found in animal foods and absorbed with the help of a stomach protein.
At risk: over 65, long-term metformin or acid-suppressing medicines, vegans and vegetarians, after stomach or bowel surgery.
Signs: numbness and tingling, forgetfulness, low mood, poor balance, sore tongue, anaemia. Nerve damage can become permanent if untreated.
Iron and ferritin
| Test | Shows |
|---|---|
| Ferritin | Iron stores (the most useful single test) |
| Serum iron | Momentary level, variable |
| Iron-binding capacity | Transport protein capacity |
| Transferrin saturation | How full the carriers are |
| CBC | Haemoglobin and cell size |
Ferritin can rise with inflammation, hiding a deficiency. In men and post-menopausal women, the doctor may look for gastrointestinal bleeding, so self-treating with iron can delay diagnosis.
Supplements
Start them based on results and medical advice; long-term high-dose vitamin D can cause high calcium; take iron away from tea and coffee; retest as advised.
We test vitamin D, B12, folate, ferritin and iron at home across Yalova, with appointments in Bursa, Istanbul and Kocaeli–Gebze.
