LDL cholesterol of 0.4 mmol/L should be determined on a patient-specific basis to determine whether it is a pathological condition and the severity of the condition. According to the Guidelines for Primary Care of Dyslipidemia (2019), the ideal level of LDL cholesterol is <2.6 mmol/L, the appropriate level is <3.4 mmol/L, 3.4 to 4.1 mmol/L is borderline elevated, and ≥4.1 mmol/L is elevated. Therefore, if disease is excluded, LDL cholesterol of 0.4 mmol/L is in the desirable range and is not pathologic. It should also be noted that decreased LDL cholesterol can also be seen in diseases such as malnutrition, absence of β-lipoproteinemia, cirrhosis, and hyperthyroidism. Therefore, it is recommended to consult a medical professional and, if necessary, improve liver function and thyroid function tests to determine whether the LDL is pathological and the severity of the disease. If there is any discomfort, seek medical attention promptly.