What should you know about an IgG blood test?

Immunoglobulin G, or IgG, is one type of antibody. The result may be used as part of an assessment for a particular infection, immune response or other medical question. A positive result can mean previous exposure or an immune response; it does not automatically prove that an illness is active. A negative result may be unhelpful if testing was done too early or if the wrong target was selected.

The report should be interpreted alongside the exact antibody name, laboratory reference range, symptoms, examination and other tests. Doctors may use blood work while assessing problems such as anaemia, chronic kidney disease, coeliac disease or glandular fever, but an IgG result alone does not explain every symptom.

Tell the clinician about recent illnesses, vaccinations, immune conditions, medicines and the date symptoms began. Ask what the test is intended to answer and whether preparation is needed. When the report arrives, check the target and reference range rather than judging a result from the word positive or negative alone. Do not start treatment or stop prescribed medicine because of an isolated result.

Contact a clinician for ongoing fever, worsening fatigue, unexplained weight change, persistent diarrhoea, swelling, reduced urine or symptoms that interfere with daily activities. Get urgent help for severe breathing difficulty, chest pain, fainting, confusion, heavy bleeding or rapidly worsening illness. A laboratory result should not delay care when symptoms are severe.

Ask what antibody was measured, whether the result suggests current or past exposure, what could make it inaccurate, whether another test is needed, and which symptoms should prompt a review.