Food poisoning is often diagnosed based on a detailed history, including how long you've been sick, your symptoms and specific foods you've eaten. Your doctor will also perform a physical exam, looking for signs of dehydration. Depending on your symptoms and health history, your doctor may conduct diagnostic tests, such as a blood test, stool culture or examination for parasites, to identify the cause and confirm the diagnosis.
For a stool culture, your doctor will send a sample of your stool to a laboratory, where a technician will try to identify the infectious organism. If an organism is found, your doctor likely will notify your local health department to determine if the food poisoning is linked to an outbreak.