The reference range of angiotensin I is 11 to 88 ng/L, which mainly stimulates the secretion of renin, and its value may change due to some lesions. Angiotensin is a substance in the body that constricts blood vessels and stimulates the secretion of aldosterone from the adrenal cortex, and is also involved in the regulation of blood pressure and body fluids in the body. Angiotensin is categorized into I-VII, and more is known about angiotensin I, angiotensin II, and angiotensin III in clinical studies. The main function of angiotensin I is to stimulate the secretion of adrenaline from the adrenal medulla, while angiotensin II mainly promotes vasoconstriction to raise blood pressure. In general, angiotensin Ⅰ will follow the changes in the body, such as the body has a large amount of blood loss led to a drop in blood pressure, renal blood flow will be reduced when angiotensin Ⅰ will increase, when there is a long-term renal vascular stenosis, will also make angiotensin Ⅰ increase. When angiotensin Ⅰ test shows obvious abnormality, it is necessary to actively consult the doctor to clarify the cause of the disease and then carry out targeted treatment.