Do you need to check so many things just for blood sugar?

In clinical work, apart from clinical manifestations, the diagnosis and treatment standards for various diseases are mostly test values. For example, in diabetes, there are fasting blood glucose, postprandial blood glucose, dynamic blood glucose, insulin release test, C-peptide release test... What exactly are these for?

 

Blood sugar

fasting blood glucose

Fasting blood glucose (FBG) is a commonly used and important indicator for diagnosing glucose metabolism disorders. It refers to the blood glucose value measured by blood collection before breakfast after overnight fasting (fasting for at least 8 to 10 hours), which can reflect the function of pancreatic β-cells and represent the secretion function of basal insulin.

Blood glucose 2 hours after meal

Oral Glucose Tolerance Test OGTT 2-hour blood glucose is also known as postprandial blood glucose. In normal people, blood sugar reaches its peak at <140 mg/dL 0.5 to 1 hour after a meal, and returns to pre-meal levels in 2 to 3 hours.

Dynamic blood glucose

Monitor the dynamic changes in blood sugar for 24 to 72 hours to understand blood sugar fluctuations and detect hidden hyperglycemia and hypoglycemia, commonly known as "blood sugar Holter".

What's the point

Among the criteria for diagnosing diabetes, one of the following is enough:

 

(1) Symptoms of diabetes (polydipsia, polyphagia, polyuria, unexplained weight loss), plus random (any time, no deliberate skipping of meals) venous blood sugar higher than 11.1 mmol/L;
(2) Fasting blood glucose is higher than 7. 0 mmol/L;
(3) Venous blood glucose higher than 11.1 mmol/L 2 hours after OGTT;
(4) The non-fasting glycated hemoglobin test value is greater than 6. 5%.

 

 

Insulin function test

Mainly include OGTT, insulin release test, C-peptide release test.

OGTT

That is, the oral glucose tolerance test. OGTT should be performed in the early morning. After fasting blood is drawn (used to measure fasting blood glucose), 75 g of glucose is mixed with 250-350 mL of water, and the subject is required to drink it within 5 minutes.

Start timing from the first oral intake, and take venous blood to measure blood sugar at 30 minutes, 1 hour, 2 hours, and 3 hours. The amount of sugar that children take varies, based on 0.75 g per kilogram of body weight, and the total amount of sugar should not exceed 75 g.

C-peptide release test

C-peptide is a peptide substance formed by the splitting of proinsulin. Its half-life is 2 to 3 times that of insulin. The concentration of C-peptide in the blood can better reflect the reserve function of pancreatic islet β cells.

The fasting C-peptide level is about 0.3-1.3 mmol/L, and peaks 30 minutes-1 hour after oral administration of glucose. The peak value is 5-10 times that of fasting C-peptide.

insulin release test

During the OGTT, an insulin release test can be performed at the same time, which can reflect the pancreatic β-cell reserve function. T1DM shows that insulin levels remain very low after glucose stimulation, showing a low and flat curve. In T2DM, fasting insulin may be normal or elevated, with delayed release after glucose stimulation.

If the insulin level does not rise significantly or appears low after glucose stimulation, it indicates low β-cell function.

The specific operation method is to measure the changes in serum insulin and C-peptide concentrations on an empty stomach and at 30 minutes, 1 hour, 2 hours and 3 hours after oral administration of glucose.

Fasting insulin levels are generally 5 to 20 mU/L. In OGTT, the insulin peak occurs 30 minutes to 1 hour after oral glucose administration. The peak should be 5 to 10 times that of fasting insulin, and returns to the fasting level after 3 hours.

Glucose in urine

Positive urine glucose is an important clue for diagnosing diabetes, but its reliability is not particularly strong.

The normal renal glucose threshold is 8.9-10.0 mmol/L. Some patients have a lowered renal glucose threshold due to renal disease. Although the blood glucose concentration is normal, they may still have glucose in the urine, which is seen in renal glycosuria. In addition, glycosuria can also occur if a large amount of sugary food is consumed and the blood sugar concentration temporarily exceeds the renal glucose threshold.

At this time, fasting blood glucose and glucose tolerance tests should be measured. If it is a normal person, these two should be normal.

In addition, you cannot stop collecting urine just because urine sugar is not as reliable as blood sugar. In addition to urine sugar, many other indicators such as urine ketones and urine protein can help diagnose and differentially diagnose other diseases.