Diagnosis of Food Poisoning

Food poisoning is diagnosed clinically and your doctor will not recommend any tests if the symptoms are mild to moderate. Most people with food poisoning improve with treatment in a few days at home and may not even need to visit a doctor.

You may need to consult a doctor for a diagnosis if:

• your symptoms are severe and you feel sick
• you are not getting better with self care and treatment at home
• you have symptoms suggestive of severe dehydration (such as sunken eyes, reduced frequency of urination, feeling dizzy or light-headed)
• there has been an outbreak of food poisoning.

Medical history and physical examination: To diagnose the cause of food poisoning, the doctor will take a detailed history and do physical examination. The doctor may ask questions such as:

• do you think you could have eaten contaminated food or liquid (did you eat anything from out as it is often the cause of food poisoning)?
• do any of your close contacts have similar symptoms?
• how many motions or vomiting do you have in a day?
• for how many days have you had the symptoms?
• do you have fever?
• is there blood or mucus in the stool?
• have you taken any medication?

The doctor will examine you to look for signs of dehydration and possible complication because of dehydration such as low blood pressure, poor peripheral pulses, and blood infection (sepsis). In infants, the doctor will examine the soft spot on the head (fontanelle) to look for dehydration (it becomes sunken if the infant is dehydrated).

Stool sample: Tests are usually not done in people with food poisoning.  The doctor may recommend stool sample to investigate for bacteria or parasites if:

• symptoms of food poisoning are severe (such as blood or pus in stool, you become dehydrated)
• your symptoms lasts more than a week
• you have high fever
• you are at risk of developing complication because of your other medical problems such as  weakened immune system, (such as due to HIV/AIDS), diabetes.

Blood tests: Blood tests are usually done if the symptoms are severe and you are admitted in a hospital. Tests may be done to rule out complications due to dehydration such as electrolyte imbalance, increase in blood urea, low blood sugar (more common in young children), and infection in blood (sepsis).