Nausea, diarrhoea and fatigue

An infection, contaminated food or a temporary food intolerance can irritate the gut and cause loose stools and nausea. Fatigue may follow fluid and electrolyte loss, poor sleep or reduced food intake. Coeliac disease can cause recurring digestive symptoms, while anaemia, chronic kidney disease and some long-term conditions may contribute to tiredness. COVID-19 can include digestive symptoms as well as fatigue. Burnout or alcohol-related illness may also affect energy, but symptom patterns overlap, so a diagnosis cannot be made from this combination alone.

Take frequent small sips of water or an oral rehydration drink, especially after a loose stool. Eat small portions of simple foods when hungry and avoid alcohol, very fatty meals and foods that clearly worsen symptoms. Rest, wash hands carefully and avoid preparing food for others while unwell. Record the start time, stool changes, vomiting, urine output, recent meals, travel and medicines. Do not start antibiotics or anti-diarrhoeal medicine without advice, particularly if there is blood, severe pain or a high temperature.

Seek urgent help for confusion, fainting, severe weakness, very little urine, blood or black stool, severe abdominal pain, or repeated vomiting that prevents drinking. Arrange medical review if diarrhoea continues, fatigue is marked, symptoms recur, or you have kidney disease, are pregnant, or take medicines that affect fluid balance. A clinician may check hydration, examine you and request stool or blood tests when needed.

Could this be infection, food intolerance or a medicine effect? Do I need blood tests for anaemia, kidney function or coeliac disease? Which fluids and foods are appropriate for me? When can I safely return to work or exercise?