Elevated serum LDH (lactate dehydrogenase) requires vigilance for lymphoma, which can present with elevated serum LDH. Lactate dehydrogenase is a class of NAD-dependent kinases that are widely found in human tissues, with much higher levels in the kidneys, followed by myocardium and bone, and LDH in red blood cells is about 100 times higher than in normal serum. Normal values in serum: 35-88 U/L (pH 8.8-9.0, 30°C). Elevation is most often seen in the following conditions: 1. myocardial infarction, peaks 36-60h after infarction. 2. Liver diseases: such as acute and chronic hepatitis, cirrhosis, hepatocellular carcinoma, obstructive jaundice, etc. 3. Blood and lymphatic system diseases: such as leukemia, malignant lymphoma, etc. 4. Skeletal muscle injury, progressive myasthenia gravis, etc. About 25% of the patients in condylomata lymphoma will have elevated serum LDH, so they need to be alert to lymphoma. If patients have elevated serum LDH, it is recommended to consult hospitals for relevant examinations to check whether there are lymphomas and other diseases.