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Fasting blood sugar

FASTING, SLEEP, AND BLOOD SUGAR

Metabolism tests include fasting blood sugar, fasting insulin and glycated hemoglobin. All of these are closely involved in blood sugar regulation. When fasting during waking hours, blood sugar levels fall steadily. Conversely, blood sugar levels usually remain constant during sleep. This is due to the blood sugar level initially rising by approximately 20 % at the beginning of the sleep cycle and then slowly falling to a normal level. These observations indicate that glucose utilization for energy is decreased during sleep. During non-REM sleep, the brain's glucose metabolism decreases by 11 %. Conversely, glucose metabolism is increased during REM sleep and when awake.


Sleep deprivation has a significant impact on blood sugar regulation. Being significantly sleep-deprived (four hours of sleep per night) for as little as a week impairs the use of glucose for energy and raises fasting blood sugar. It is also a predisposing factor for sugar metabolism disorders (pre-diabetes). According to a study, individuals who sleep less than 6.5 hours per night have up to 40 % lower insulin sensitivity than those who get a normal amount (7–8 hours) of sleep per night. Impaired insulin sensitivity is a predisposing factor for blood sugar swings, obesity, and type 2 diabetes.

FASTING BLOOD SUGAR (FPG)

Glucose is the primary cellular energy source. The glucose levels in the plasma reflect the glucose intake from food, the breakdown of liver and muscle glycogen and the glucose produced via gluconeogenesis. High fasting glucose levels may be caused by insulin resistance, severe acute stress or certain illnesses. Glucocorticoid drugs also raise the glucose level. Low fasting glucose levels occur after fasting for several days or are associated with certain medical conditions or excessive insulin doses.

  • Reference range: 4–6 mmol/L
  • Optimal: 4.0–5.3 mmol/L
  • Recommended by the Life Extension Foundation: 4.0–4.7 mmol/L

An extensive study of Korean adults (n=12,455,361) found that the fasting glucose levels associated with the lowest mortality were 4.0–5.2 mmol/l (80–94 mg/dL). High fasting blood sugar levels may be a predisposing factor for various diseases such as cancer, cardiovascular diseases, Alzheimer's disease, kidney disease, pancreatic insufficiency, retinal damage or neuropathy. This is why maintaining a normal fasting blood sugar level is important for your general health. Isolated high values may occur in connection with acute stress. This should be taken into consideration when interpreting the results.