Dehydration fever is a phenomenon in which the body temperature rises after severe dehydration, especially in children, due to a decrease in water evaporation from the skin, which affects the body’s ability to dissipate heat. Examination: Patients with dehydration fever need to undergo general examination first, and then decide on further examination items according to the general screening results, and try to avoid aimless “scattering” examination. Blood, urine and fecal tests are the first choice to confirm the diagnosis of dehydration fever. An increased total white blood cell count and neutrophil count are considered bacterial infections, while a decreased count is more likely to be a viral or bacillary infection. If sepsis, intestinal and urinary tract infections are suspected, blood, fecal and urine cultures should be sent respectively. In addition to the routine examination of various puncture fluids, sometimes it is necessary to send culture or smear examination. For example, meningococci can be found in skin petechiae and cerebrospinal fluid smears in patients with epidemic meningomyelitis, Plasmodium can be found in blood smears in children with malaria, and diphtheria pseudomembrane smears can be examined for Corynebacterium diphtheriae. Patients with dehydration fever need to check for Fertilizer reaction, exophthalmic reaction, heterophilic agglutination test, and condensation set test if necessary, which can help in differential diagnosis. Anti-streptococcal hemolysin O or rheumatoid factor tests are performed for rheumatic fever or rheumatoid disease, respectively. If viral infection is suspected, early rapid diagnostic tests in immunology are feasible.