The causes of fever are complex. The need for relevant investigations depends on the duration of the fever rather than the height of the fever. Any fever checked after 3 days is recommended for appropriate investigations. Because children are not very expressive, sometimes a fever of no more than 38.5°C does not mean that the condition is not serious and blood tests and C-reactive protein are still recommended. An experienced paediatrician will be able to take into account the test values to determine the condition and the possibility of subsequent changes in the condition and to provide early preventive treatment to avoid paediatric febrile convulsions.