Blood test for diphtheria: what to know

Diphtheria can cause a sore throat, fever, swollen neck glands, weakness, or a thick coating in the throat. Skin infection can produce a sore that does not heal. Clinicians may take a swab from the throat, nose, or skin lesion for laboratory testing. Blood work can show how the illness is affecting the body, but it does not replace the relevant sample. Because the toxin can damage the heart and nerves, treatment decisions may begin before every laboratory result is available.

Contact a healthcare service urgently if diphtheria is suspected, and tell staff before arrival so they can advise about infection precautions. Avoid close contact, sharing utensils, and preparing food for others until a clinician gives instructions. Do not wait for a blood-test appointment or try to treat a throat coating yourself. The clinical team may discuss antibiotics, antitoxin, monitoring, and testing of close contacts.

Seek emergency help for difficult or noisy breathing, inability to swallow saliva, rapidly increasing neck swelling, bluish lips, fainting, chest symptoms, or severe weakness. A persistent sore throat with fever or a grey-white coating also needs prompt assessment, particularly after possible exposure or when vaccination is uncertain. These symptoms require urgent evaluation and do not establish the diagnosis by themselves.

Which sample should be tested? Do I need isolation advice? Should close contacts be assessed? What symptoms would mean I need emergency care? Is my vaccination record up to date?