Influenza can be detected by blood test, but it still needs to be combined with other symptoms, signs and auxiliary tests to make a definite diagnosis. Influenza is caused by influenza virus infection, which can cause symptoms such as chills, high fever, headache, body aches and weakness. In terms of blood tests, there are certain specific manifestations. Peripheral blood routine may show a normal or low total white blood cell count and a relative increase in lymphocytes. Serologic tests may show elevated anti-influenza virus antibody titers of 4-fold or more. The patient’s respiratory epithelial cells are checked for influenza virus antigens and may show positivity. Influenza virus can be isolated through rhinitis secretions and lower respiratory secretions, which can contribute to the symptoms of the disease. Influenza can be detected by blood test, but it has certain false-positive or false-negative, and it is recommended to consult a doctor in time and make a comprehensive diagnosis under the guidance of a specialized doctor and with the combination of clinical information.