The first and most commonly reported manifestation of gastroenteritis is loose, frequent stool (diarrhea). Episodes can occur repeatedly over the day and are associated with loss of fluids. Descriptions in clinical sources note that fluid and electrolyte loss accompanies increased stool output. During periods of active symptoms, absorption of nutrients and water may be reduced, and electrolyte-containing beverages are often discussed in educational materials as part of general background information on hydration.
People with gastroenteritis frequently describe pronounced tiredness and a sense of reduced energy. This is attributed to the combined effects of illness, altered intake, and fluid losses. Rest does not always restore energy while symptoms are ongoing. Fatigue is nonspecific and occurs in many conditions; when it appears together with diarrhea and other gastrointestinal features, it is commonly mentioned in summaries of gastroenteritis presentations.
Abdominal cramps are often reported during episodes of gastroenteritis. Individuals may note diffuse cramping or sharper pains across the abdominal area. Intensity varies over time and among people. Because cramping can also follow exertion or other benign triggers, clinical descriptions emphasize context and accompanying signs when characterizing gastroenteritis.
Fever is described in a subset of cases. The body’s response to infection can include elevated temperature with chills. Educational sources note that temperatures may reach 102°F (39°C) or higher in some instances and can persist for several days. Early symptoms may resemble other febrile illnesses, and progression is often monitored alongside gastrointestinal signs.
Nausea and vomiting are additional features documented with gastroenteritis. Like diarrhea, recurrent vomiting contributes to fluid and electrolyte loss. “Stomach flu” is a colloquial term sometimes used for viral gastroenteritis that presents with both diarrhea and vomiting. Reports describe onset after exposure to contaminated food or contact with an ill individual, followed by varying degrees of nausea.
Headache may occur during illness. It is not limited to the abdomen or stomach region; systemic symptoms are frequently noted. Contributors discussed in literature include fever, dehydration, and general systemic responses. Descriptions remain nonspecific because similar headaches can appear in many viral syndromes.
Generalized muscle aching (myalgia) is commonly mentioned in overviews of viral gastroenteritis. Individuals may describe soreness in the arms or legs and transient reduction in usual strength during illness. Severe inflammatory muscle disease (myositis) is not typical, whereas short-lived aches are more frequently reported.
Stool appearance can change during gastroenteritis. Some people report visible blood or darker discoloration, though causes vary and are not specific to one condition. In clinical writing, the presence, quantity, and color are documented as part of the overall assessment alongside other signs and history.
Lethargy—a marked lack of energy and increased drowsiness—is described during active illness. Stress, workload, and inactivity can also contribute to this sensation. In gastroenteritis, energy levels often reflect the combined impact of reduced intake, sleep disruption, fever, and fluid loss while the body responds to infection.
Dehydration represents a downstream effect of persistent diarrhea and vomiting. Overviews characterize dehydration by signs such as dry mouth, decreased skin moisture, lightheadedness, fatigue, and, in some cases, reduced tear production. Educational materials commonly reference the role of fluids and electrolytes in maintaining balance during gastrointestinal illnesses.
Learn more about gastroenteritis at National Institute of Diabetes and Digestive and Kidney Diseases.