Blood tests for loss of appetite investigation
| Test | What it checks for |
|---|---|
| CBC | Anaemia (cancer, chronic disease); infection; malignancy clues |
| CRP / ESR | Active inflammation or malignancy |
| LFT (albumin, bilirubin, ALT) | Liver disease — hepatitis, cirrhosis; low albumin = malnutrition |
| Creatinine / eGFR | Kidney failure causes uraemic anorexia and nausea |
| TSH | Hypothyroidism (slows metabolism, reduces appetite) or hyperthyroidism |
| Calcium | Hypercalcaemia causes anorexia, nausea and confusion |
| Glucose / HbA1c | Uncontrolled diabetes can suppress appetite |
| HIV test | Advanced HIV/AIDS causes wasting and anorexia |
| LDH + SPEP | Malignancy screen — lymphoma, myeloma |
| PSA (men over 50) | Prostate cancer presenting with weight loss |
When is loss of appetite a warning sign?
Seek medical attention if appetite loss is accompanied by:
- Unintentional weight loss >5% body weight over 6 months
- Difficulty swallowing (dysphagia)
- Persistent abdominal pain
- Night sweats and fever
- Lump in the neck, armpit or groin
- Jaundice (yellow eyes or skin)
- Blood in stool or black/tarry stools
Common causes of loss of appetite
Depression and anxiety
Mental health conditions are among the most common causes of appetite loss. Depression reduces motivation and pleasure around food; anxiety can cause nausea. Blood tests are normal. Treatment: talking therapies, antidepressants.
Medications
Many medications reduce appetite as a side effect: metformin, antibiotics, chemotherapy, opioids, stimulants (ADHD medications, decongestants), digoxin, topiramate and many others. Review all current medications.
Liver and kidney disease
Liver disease causes nausea, bitter taste and appetite loss from bile acid accumulation. Kidney failure causes uraemia — build-up of waste products that cause profound anorexia, nausea and metallic taste. LFT and renal function are essential tests.
Thyroid disease
Hypothyroidism slows the entire metabolic rate, reducing appetite. Paradoxically, severe hyperthyroidism (thyroid storm) can also cause anorexia alongside weight loss. TSH is the key test.
Cancer
Unexplained weight loss and appetite loss ('cancer anorexia-cachexia syndrome') can be the presenting symptom of any malignancy. Particularly concerning when accompanied by the warning signs above. A full blood count, LFT, CRP, calcium and PSA (in men) are the initial screen.
Questions to ask your doctor
- How much weight have I lost and over what period?
- Should I be screened for cancer?
- Could depression be contributing?
- Are any of my medications causing this?
- Do I need a CT scan or endoscopy?