Blood tests ordered for nausea and vomiting
| Test | What it checks for |
|---|---|
| Electrolytes (Na, K, Cl, HCO3) | Dehydration, low potassium and alkalosis from vomiting |
| Glucose / ketones | Diabetic ketoacidosis (DKA) or hypoglycaemia |
| Amylase / lipase | Acute pancreatitis |
| LFT (bilirubin, ALT, ALP) | Hepatitis, gallstones, liver disease |
| Beta-hCG (pregnancy test) | First trimester morning sickness; ectopic pregnancy |
| Creatinine / eGFR | Kidney failure causes nausea |
| Calcium | Hypercalcaemia causes nausea, constipation and confusion |
| TSH | Thyroid disease (both hypo and hyperthyroid can cause GI symptoms) |
| CRP / procalcitonin | Infection — appendicitis, gastroenteritis, meningitis |
Common causes of nausea and vomiting
Gastroenteritis (stomach bug)
Viral or bacterial gut infection — the most common cause of acute nausea and vomiting. Usually self-limiting (24–72 hours), associated with diarrhoea, crampy abdominal pain, sometimes low-grade fever. Blood tests usually normal. Treatment: hydration, rest, antiemetics if needed.
Pregnancy (morning sickness)
Nausea and vomiting affecting up to 80% of pregnant women, typically in the first trimester. Hyperemesis gravidarum is the severe form requiring hospitalisation. Beta-hCG is the first test if pregnancy is possible. Electrolytes, urine ketones and LFT should be checked in hyperemesis.
Diabetic ketoacidosis (DKA)
In type 1 diabetes (and sometimes type 2), severe insulin deficiency causes the body to break down fat for energy, producing ketones. DKA causes nausea, vomiting, abdominal pain, fruity breath, rapid breathing and confusion. Blood glucose is very high (>250 mg/dL); ketones are positive; bicarbonate is low (acidosis). Medical emergency.
Acute pancreatitis
Severe, constant upper abdominal pain radiating to the back, with nausea and vomiting. Amylase and lipase markedly elevated (>3x upper limit). Most commonly caused by gallstones or alcohol. May be severe — check CRP after 48 hours (CRP >150 suggests severe pancreatitis).
Medications — extremely common cause
NSAIDs, opioids, antibiotics, metformin, digoxin, chemotherapy, iron supplements and many other medications cause nausea and vomiting as a side effect. Review all medications including over-the-counter drugs.
Raised intracranial pressure
Brain tumour, hydrocephalus or meningitis can cause projectile vomiting (without preceding nausea) and severe headache, worse in the morning. This is a red flag — requires urgent imaging.
Questions to ask your doctor
- Is there a pregnancy to exclude first?
- Are my electrolytes normal?
- Should I check amylase/lipase for pancreatitis?
- Is a medication causing this?
- Do I need IV fluids for dehydration?