Since there are no obvious clinical symptoms in the early stage of diabetic nephropathy, only the glomerular filtration rate can increase by 20-40%, and this “hyperfiltration” state can only be detected by special tests, so it is difficult to be used as a routine clinical test to screen diabetic patients for early diabetic nephropathy. However, when the glomerular filtration rate increases significantly, the volume of the kidney will also increase, and the blood flow in the renal artery will also increase. Therefore, at this time, ultrasound Doppler technology can be applied to detect abnormalities at the earliest possible time, but it is only meaningful to compare the precise values before and after the onset of the disease in that patient himself. In healthy individuals and in early diabetic nephropathy states, there is no or only a very small amount of protein present in the urine, called protein-free or normal proteinuria. In fact, the rate of albumin excretion by the kidney is significantly increased at the same time as the glomerular filtration rate is increased. Modern biochemical and immunoassay techniques can accurately determine the level of microalbumin in urine, so it provides an important tool for early detection of diabetic nephropathy, making this kidney pathological change of increased albumin excretion rate, which was clinically insidious, clinically detectable. Therefore, diabetic patients must be tested regularly for urinary protein excretion, which is currently the main means of early detection of early diabetic nephropathy, preferably by retaining urine for 24 hours to quantify albumin in the urine. The best way to retain urine is to empty the bladder in the morning after waking up, treat and eat normally that day, do not do strenuous exercise or heavy physical work, collect all the urine from the second urine to the first urine after waking up the next day, measure the total volume or weight and record it, then mix and take 10-15 ml urine sample to the hospital for testing. Currently, by accurately measuring the amount of albumin excreted in the urine, patients with diabetic nephropathy are internationally classified into three tiers, namely, no proteinuria or normal proteinuria (24-hour urine protein less than 30 mg); microproteinuria (24-hour urine protein between 30 and 299 mg); and clinical proteinuria (24-hour urine protein equal to or greater than 300 mg). If it is difficult to collect 24-hour urine, a random “spot urine” can also be used to determine the amount of urinary protein excretion, but the amount of creatinine elimination in the urine must be measured at the same time, and the ratio of the two is used to correct for this, because the filtration state of the glomerulus also has a circadian rhythm and is affected by other factors, but of course this correction is also limited to renal function. This correction is, of course, limited to patients with diabetic nephropathy with essentially normal renal function in the stratum of microproteinuria and clinical proteinuria. Expressing urinary protein excretion in micrograms and urinary creatinine excretion in milligrams, the ratio of urinary protein to urinary creatinine is equivalent to the above data in classifying the three strata of diabetic nephropathy, i.e., normal proteinuria less than 30 micrograms per milligram of creatinine; microproteinuria between 30 and 299 micrograms per milligram of creatinine; and clinical proteinuria equal to or greater than 300 micrograms per milligram of creatinine. In the case of urinary protein excretion measured by a 24-hour urine, we can also calculate the rate of excretion of albumin per minute in the urine. Normal proteinuria is less than 20 micrograms per minute; microproteinuria is between 20 and 199 micrograms per minute; clinical proteinuria is equal to or greater than 200 micrograms per minute. Monitoring of urinary albumin is important not only for understanding the development of diabetic nephropathy, but also as a predictor of the degree of risk of coronary heart disease. Unfortunately, about 10-25% of patients with type 2 diabetes already have microproteinuria at the time of diagnosis, and a few already have clinical proteinuria present.