Blood too thick may be high blood viscosity or high blood lipids or elevated hemoglobin, which may be caused by: 1, drinking too little water and consuming too much fat and protein foods, causing blood stagnation; 2, obesity, high body mass index, and insufficient effective circulating blood; 3, high lipid-related indicators, such as high total cholesterol, high triglycerides, low HDL cholesterol, and high LDL cholesterol, which is also known as abnormal lipid metabolism; 4, certain blood system diseases, such as hemophagocytic syndrome, certain types of leukemia, multiple myeloma and other diseases, causing abnormal hemoglobin, elevated or lower, if elevated, that is, resulting in too thick blood, accelerated hematocrit. In conclusion, blood is too thick is not a clinical term, and the specific cause needs to be perfected with relevant laboratory tests.