What to expect from a blood test for Crohn's disease

Tests may include a blood count, inflammatory markers, iron and vitamin levels, electrolytes, liver tests, and kidney tests. These results can help show how active an illness may be and whether ongoing bowel symptoms have affected hydration or nutrition. Blood tests cannot identify every cause of abdominal pain or prove Crohn's disease on their own. Results are considered with bowel symptoms, examination, stool testing, scans, or an endoscopic assessment when needed.

Check whether fasting is needed for the particular group of tests and tell the clinician about medicines, supplements, recent infections, bleeding, diarrhoea, and dietary restrictions. Do not stop prescribed treatment unless instructed. Bring details of symptoms, including stool changes, pain, fever, and weight change, because they help place the result in context. The sample is taken with a needle and brief soreness or bruising is possible.

Seek prompt medical advice for persistent bloody diarrhoea, worsening abdominal pain, fever, repeated vomiting, or inability to keep fluids down. Get urgent help for severe pain with a swollen abdomen, fainting, heavy rectal bleeding, or signs of dehydration. Do not wait for routine blood-test results when these symptoms occur.

Which inflammation and nutrition markers will you check? Could my medicines change the results? Do I need stool testing or imaging as well? When will we review the findings and decide on the next investigation?