Blood tests for memory loss
| Test | Why ordered | Treatable if abnormal? |
|---|---|---|
| TSH | Hypothyroidism — cognitive slowing, confusion | Yes — thyroid hormone replacement |
| Vitamin B12 | B12 deficiency dementia — a reversible cause | Yes — B12 injections or supplements |
| Folate | Folate deficiency — cognitive impairment | Yes — folic acid supplements |
| Fasting glucose / HbA1c | Diabetes affects brain function | Yes — blood sugar control |
| FBC | Anaemia — reduces oxygen to the brain | Yes — treat underlying cause |
| Calcium | Hypercalcaemia causes confusion | Yes — treat calcium disorder |
| LFT | Hepatic encephalopathy | Yes — treat liver disease |
| Syphilis serology (RPR/VDRL) | Neurosyphilis — rare but treatable | Yes — antibiotics |
When memory loss is more than normal ageing
Warning signs that need urgent assessment
Normal age-related memory changes include occasionally forgetting names or misplacing objects but remembering them later. Concerning features that need prompt evaluation: forgetting recently learned information repeatedly; getting lost in familiar places; difficulty with everyday tasks (managing finances, cooking); personality or behaviour changes; confusion about time, place or people; repeating the same question multiple times in the same conversation.
Dementia — when blood tests are normal
If all blood tests are normal but significant memory impairment persists, the most common diagnoses are Alzheimer's disease (60–70% of dementias), vascular dementia, Lewy body dementia, or frontotemporal dementia. Further investigation may include: cognitive testing (MMSE, MoCA), brain MRI, and in specialist centres, PET scan or cerebrospinal fluid biomarkers (amyloid, tau). Referral to a memory clinic or neurologist is recommended.
Questions to ask your doctor
- Have reversible blood test causes been ruled out?
- Should I have a formal cognitive assessment?
- Do I need a brain MRI?
- Should I see a memory clinic or neurologist?