Low fever and temperature measurement is slightly different for each person’s normal body temperature, which is generally around 36.5 to 37 degrees, and a low fever cannot be considered as just 37 or 38 degrees. Generally, a fever is considered to be low when the body temperature measured is about 0.3 to 0.6 degrees higher than the normal body temperature. At the same time, there may be small differences in the temperature measured in different seasons or at different times of the day. In addition, we should also pay attention to the time and method of taking the temperature, the best time to take the normal temperature in the morning. In other words, it is best to take the temperature in the morning, when you are still in bed, when you have not even gone to the toilet to pee or wash your clothes. An axillary body temperature greater than 37 and less than 38 degrees is considered a low fever. Fever is only a clinical symptom. It must be combined with clinical to have a specific meaning. If it is just a cold and low fever do not need special treatment, drink more water, light diet can be. According to your situation do not worry too much, you can drink more water and sweat more, which will help to bring down the fever. If the body temperature reaches 38.5 or more, then you should take the relevant drugs to reduce fever under the guidance of a physician, eat a light diet recently and pay attention to rest. We often see and hear about high fevers, but low fevers are less common compared to high fevers, especially persistent low fevers. Because it is usually rare, it is more worthy of our attention and prevention. We need to find out the reason for the occurrence of persistent low fever so that we can prescribe the right medicine and find the root cause to cure the disease. Generally speaking, the normal body temperature of the human body is around 36-37 degrees, the temperature is higher in the afternoon, and the body temperature can rise slightly after strenuous exercise, labor, and meals, but generally fluctuates no more than 1 degree. The body temperature of women before menstruation and during pregnancy is slightly higher than normal, and the body temperature can also be slightly higher under emotional tension and excitement and high temperature environment. A low fever of 37.3-38 degrees is considered to be hypothermia. 1, tuberculosis is a common cause of hypothermia, pulmonary tuberculosis is common, early asymptomatic signs and symptoms in time for chest X-ray examination. The next is extrapulmonary tuberculosis, such as liver and kidney, intestine, mesenteric lymph nodes, pelvis, bone and joint tuberculosis, etc. In addition to local symptoms, there are often toxic symptoms of tuberculosis, increased blood sedimentation tuberculin test strong positive, anti-tuberculosis treatment has a definite effect, which helps to diagnose the elderly tuberculosis symptoms are not obvious, its pulmonary complications, tuberculin test negative easily diagnosed as chronic bronchitis or asthma. Therefore, in case of elderly people with persistent cough, sputum and cold, ineffective treatment with anti-inflammatory drugs, low fever and weakness, sputum tuberculosis (smear or TB-PCR) and chest X-ray should be examined promptly. The elderly are prone to extra-pulmonary tuberculosis such as tuberculous meningitis, pleurisy, peritonitis, bone, kidney, lymph node tuberculosis, etc. 2. Chronic nephrolithiasis is a common cause of hypothermia in female patients. There may be no obvious symptoms, signs and even urine examination without abnormalities, with hypothermia as the only manifestation. Timely detection of urine cell count early in the morning for the first time in the middle urine culture and colony count, such as urine leukocytes > 5/HP, positive bacterial culture, colony count > 105 can confirm the diagnosis. 3, chronic focal infections such as paranasal sinusitis, gum abscess, prostatitis, biliary tract infection, chronic pelvic inflammatory disease, etc.. Irregular low fever is often seen with local symptoms and signs, and the symptoms disappear when the lesion is cleared. 4, AIDS (AIDS) is a systemic disease caused by the human immunodeficiency virus (HlV) that invades and destroys the human immune system, damaging multiple organs. It can be transmitted sexually through blood and body fluids. The clinical manifestations are complex, but the basic feature is that HlV causes impairment of human cellular immunity, leaving the body in a state of severe and progressive immunodeficiency, which is complicated by various opportunistic infections and malignant tumors, manifested by long-term irregular fever, chronic diarrhea for more than 1 month, ineffective to general antibiotic treatment, wasting, general lymph node enlargement of unknown cause, repeated bacterial fungal and protozoal infections, combined with epidemiological data Timely anti-HlVP24 shake antigen test. 5, cytomegalovirus infection can persist in low fever, similar to infectious mononucleosis, viral hepatitis based on anti-CMVIgM test diagnosis. 6, hyperthyroidism manifests early hypothermia with palpitations, rapid pulse, hyperhidrosis, hyperappetite, emaciation, hand tremors, enlarged thyroid gland, local murmur, etc. T3T4, rT3, etc. are measured. For hyperthyroidism without protrusion, 131I uptake test should be performed to exclude elevated T3 and T4 levels in the blood due to hormonal overflow in thyroiditis. 7, malignant tumors in middle-aged people with unexplained low fever and increased blood sedimentation should pay attention to tumor examination, such as primary liver cancer. Lung cancer, kidney cancer and colon cancer, etc. 8, neurofunctional hypothermia is mostly seen in young women, and is obvious in summer. The difference in body temperature between one day 9, post-infection hypothermia acute bacterial or viral infection control, but still have low fever, fatigue lack of appetite, etc., and the patient’s plant nervous disorders. These are the causes of persistent low fever, after understanding these, we can reasonably judge whether it is a low fever in the face of these symptoms above. Low fever can occur at different ages, so we should all pay attention to it, whether it’s our family or ourselves, and go to the hospital in time to avoid delaying the best treatment time or causing other diseases.