Symptom Guide

Loss of Appetite (Anorexia)

Name: Loss of Appetite: Causes & Blood Tests | HealthReview
Creator: Suman Konda
Published: 2026-07-05

Persistent loss of appetite, especially when combined with unintentional weight loss, can be a sign of serious underlying illness. Blood tests are the key first step in investigation.¹

Written by Suman Konda, PharmD, Clinical Pharmacist · Editorial policy · Not medical advice

Last updated: 01 August 2026 · How we check our content

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?

References

Sources cited on this page. PubMed links open the original abstract.

Donini LM, Savina C, Cannella C. Eating habits and appetite control in the elderly: the anorexia of aging. Int Psychogeriatr. 2003;15(1):73–87. PMID 12834202 · doi:10.1017/s1041610203008779

Physiological versus pathological loss of appetite

Appetite is regulated by a complex interaction between gut hormones (ghrelin – the hunger hormone; GLP-1 and PYY – satiety signals), the hypothalamus, and higher brain centres. A temporary loss of appetite during illness is a normal adaptive response – inflammatory cytokines (particularly IL-1β and TNF-α) suppress appetite to redirect metabolic energy toward immune function. This becomes pathological when it is persistent, out of proportion to any identifiable illness, or accompanied by significant involuntary weight loss.

Clinically significant anorexia (loss of appetite) lasting more than 4 weeks with unintentional weight loss of more than 5% of body weight warrants systematic investigation. The differential is broad: cancer, infection, medication side effects, depression, and metabolic disorders are the most common causes.

Blood tests used to investigate persistent loss of appetite

Full blood count (FBC): Anaemia – particularly iron deficiency anaemia or the anaemia of chronic disease – is both a cause and consequence of poor appetite. Raised white cells suggest infection; abnormal white cell differential may indicate leukaemia or lymphoma.
ESR and CRP: Non-specific inflammatory markers. A markedly elevated ESR (above 50 mm/hr) in an older person with weight loss and poor appetite warrants urgent investigation for occult cancer, tuberculosis, or vasculitis.
LFTs (liver function tests): Liver disease – whether hepatitis, cirrhosis, or liver metastases – commonly causes nausea and anorexia. Raised bilirubin plus anorexia suggests hepatic or biliary pathology.
Calcium: Hypercalcaemia causes nausea, constipation, fatigue, and anorexia – the "moans, groans, stones, and bones" mnemonic. Causes include primary hyperparathyroidism and malignancy (particularly squamous cell lung cancer, multiple myeloma, and breast cancer with bone metastases).
TSH: Both hypothyroidism (via fatigue and metabolic slowing) and hyperthyroidism (via increased metabolism and anxiety) can alter appetite, though the mechanisms differ.
Urea and creatinine: Uraemia (kidney failure) causes profound anorexia, nausea, and a metallic taste – one of the symptoms driving the decision to start dialysis.
Blood glucose / HbA1c: Uncontrolled diabetes causes nausea and anorexia when ketoacidosis develops, or via gastroparesis (delayed stomach emptying) – a common diabetic complication.

Medications as a leading cause

Before extensive investigation, a thorough medication review is essential. Medications causing anorexia include: opioids (nausea and constipation impair intake), GLP-1 receptor agonists (semaglutide, liraglutide – appetite suppression is the therapeutic mechanism), metformin, NSAIDs, SSRIs, digoxin (a classic cause of anorexia in toxicity), and many chemotherapy agents. Identifying a drug cause eliminates the need for further investigation.