Fasting glucose (fasting blood glucose) (synonyms: Fasting glucose, blood glucose value, blood glucose (BG); blood glucose) is used to detect impaired glucose utilization and in the early diagnosis of diabetes mellitus (diabetes). It is taken after the patient has not eaten for at least eight hours beforehand; usually in the morning before breakfast.
The procedure
There are two methods of measurement:
- Enzymatic measurement method – is performed in the laboratory (wet chemistry); it is based on an enzymatic conversion of glucose.
- Reflectometric measurement method – this method is performed in self-monitoring or emergency medicine; in the process, a dye is produced or changed by the enzymatic conversion of glucose; the color change can be converted into the blood glucose value.
- For the determination of the values blood plasma / blood serum or whole blood is needed.
- Self-monitoring is performed with capillary blood from the finger or earlobe, these values are then 20-30 mg/dl higher than the values in whole blood
Both methods are very accurate. Material needed
- Fluoride tubes (sodium fluoride, NaF plasma) (recommended).
- Serum (optimal: after clotting immediately abserene, immediate forwarding to a laboratory).
- LiH and EDTA plasma possible
Do not use serum monovettes, but special monovettes with a stabilizer so that the glucose concentration does not decrease due to glycolysis. Preparation of the patient
- The patient must be fasting for at least eight hours.
Interfering factors
- Because preparations containing cinnamon can significantly lower blood glucose and increase insulin sensitivity, the use of these preparations must be refrained from 12 hours before blood sampling.
Normal values
| Plasma, venous | Whole blood (capillary, hemolyzed) | Assessment |
| < 100 mg/dl (< 5.6 mmol/l) | < 90 mg/dl(< 5.0 mmol/l) | Normal |
| 100-125 mg/dl * (5.6-6.9 mmol/l) | 90-109 mg/dl(5.1-6.0 mmol/l) | Prediabetes (impaired fasting glucose). |
| 110-125 mg/dl * * (6.1-6.9 mmol/l | k. A. | Prediabetes |
| ≥ 126 mg/dl(≥ 7 mmol/l) | ≥ 110 mg/dl(≥ 6.1 mmol/l) | Diabetic |
* American Diabetes Association definition* * WHO definition.
Conversion of units of measurement
| mg/dl x 0.0555 | = mmol/l |
| mmol/l x 18.0182 | = mg/dl |
Indications (areas of application)
- Detection of impaired glucose utilization.
- Early diagnosis of diabetes mellitus
Interpretation
- For borderline or diabetic values, baseline diabetes diagnostics are performed to rule out diabetes mellitus (diabetes). This includes a daily blood glucose profile, an oral glucose tolerance test (oGTT), and determination of HbA1c (long-term glucose level).
- A single detected occasional blood glucose ≥ 100 mg/dl in plasma is associated with a 20-fold increased risk of undiagnosed type 2 diabetes.
- If fasting plasma glucose increases between 2 blood draws approximately 3 years apart, the risk of developing type 2 diabetes increases in subsequent years. According to one study, each 9 mg/dl increase in fasting glucose increased the risk of diabetes by 19% (this also applies to glucose levels below the threshold for prediabetes).
Further notes
- Two-thirds (69%) of participants in a Framingham Heart Study cohort with abnormal fasting glucose levels did not progress beyond the prediabetes stage with a fasting blood glucose of 125 mg/dl or less throughout life; the risk of CHD-related death was lower than that of diabetic patients but higher than that of healthy patients.
