LDL cholesterol of 2.9 mmol/L is not dangerous. LDL accounts for about 2/3 of plasma lipoproteins, is a cholesterol-rich type of lipoprotein, capable of transporting cholesterol, and is often used as one of the indicators for diagnosing hypercholesterolemia, with a normal range of 2.07 to 3.37 mmol/L. The current check value of 2.9 mmol/L is within the normal range. However, if LDL is too high or too low, it is not normal. If it is high, it may be caused by stress, obesity, heredity and other factors while if it is low, it may be caused by excessive weight loss, low fat intake and so on. At present, it is recommended to still adopt a healthy lifestyle and pay attention to observing the physical condition, if there is any physical discomfort, go to the hospital in time for examination.