What is Fasting Blood Glucose?
Fasting glucose is a measure of the amount of glucose (sugar) in your bloodstream after an overnight fast of at least 8 hours. Glucose is the body's primary fuel source , it comes from carbohydrates and is managed by insulin, which signals cells to absorb it from the blood. Fasting glucose reflects how well the body maintains blood sugar stability in the absence of food intake and is one of the foundational markers of metabolic health.
Fasting glucose pairs with fasting insulin to provide a complete picture of metabolic health. While fasting glucose alone can appear normal even in early insulin resistance , because the pancreas compensates by producing more insulin , combining both allows calculation of HOMA-IR, the most widely used research measure of insulin resistance. Pre-diabetic glucose levels in the context of peptide research warrant metabolic-first evaluation before GH approaches are considered.
What do the numbers mean?
≥ 126 mg/dL (diabetes threshold)
Lab reference ranges vary by laboratory, age, sex, and testing method. Always interpret your results with your healthcare provider , do not self-diagnose based on these ranges.
Why this marker matters before peptide research.
In GH secretagogue research, fasting glucose is monitored because GH elevation transiently reduces insulin sensitivity , which can push borderline glucose levels into pre-diabetic ranges during active protocols. A research protocol initiated at fasting glucose of 95 mg/dL with high fasting insulin already present represents a meaningfully different metabolic risk profile than one initiated at 78 mg/dL with optimal insulin. Knowing both before starting any GH protocol is essential context.
In GLP-1 agonist research, fasting glucose is a primary efficacy marker. The SUSTAIN, STEP, and SURPASS trial series all documented meaningful reductions in fasting glucose alongside weight loss and HbA1c improvement with semaglutide and tirzepatide. Establishing a pre-protocol baseline enables objective measurement of glycemic response over a research protocol timeline.
The combination of fasting glucose and fasting insulin (HOMA-IR) is the most sensitive research tool for identifying insulin resistance before it becomes detectable on standard metabolic panels. The formula is: HOMA-IR = (fasting insulin in µIU/mL × fasting glucose in mg/dL) ÷ 405. A result above 2.0 suggests insulin resistance; above 2.9 indicates moderate to significant resistance. Testing both simultaneously in a single fasted blood draw provides substantially more information than either marker alone.
How to get this test.
Where to order
Standard blood draw at any major lab , LabCorp, Quest Diagnostics, or through your physician. Included in most standard metabolic panels (BMP, CMP). Order alongside fasting insulin for HOMA-IR calculation in a single fasted draw.
How to prepare
Minimum 8–12 hours fasting required , no food or caloric beverages. Water is fine. Draw in the morning before any food intake. Avoid intense exercise the morning of the draw as it transiently lowers blood glucose and may not reflect a stable baseline.
What to ask for
"Fasting Glucose" or "Fasting Blood Sugar" , included in Basic Metabolic Panel (BMP) and Comprehensive Metabolic Panel (CMP). Can also be ordered as a standalone test. Pair with "Fasting Insulin" to calculate HOMA-IR in the same blood draw.