Fasting blood sugarFBS, Fasting plasma glucoseFasting blood sugar is the glucose level in blood after at least eight hours without food or sweetened drink. It is the simplest and cheapest test for diabetes, and one of the three that can diagnose it.
Dawn phenomenon
A natural rise in blood sugar in the early morning, caused by hormones that prepare the body to wake. It makes fasting readings higher than expected.
Between roughly 3am and 8am the body releases cortisol and growth hormone, which prompt the liver to release . Everyone does this; in diabetes there is not enough to blunt it.
It explains a frustrating pattern: a good reading before bed and a high one on waking, with nothing eaten in between.
Related terms
- Basal insulinBackground insulin, Long-acting insulinLong-acting insulin that provides a steady background level through the day and night, usually injected once daily.
- HypoglycaemiaLow blood sugar, HypoBlood sugar that has fallen too low, usually below 70 mg/dL. It comes on within minutes and needs sugar immediately.