Glucagon Test: Normal Levels & What High/Low Means

What is Glucagon?

Glucagon is a peptide hormone produced by the alpha cells of the pancreas. It acts as the body's primary counter-regulatory hormone to insulin, meaning it raises blood glucose levels when they drop too low. In my clinical practice, I often see patients who are surprised to learn that glucagon is just as important as insulin in maintaining metabolic balance.

Why Measure Glucagon?

Testing glucagon levels helps diagnose rare pancreatic tumors (glucagonomas), evaluate unexplained hypoglycemia, and assess alpha-cell function in diabetes. It is not a routine test but one I order when glucose swings defy explanation or when symptoms like a rash (necrolytic migratory erythema) suggest an underlying endocrine issue.

Normal Reference Ranges for Glucagon

Reference intervals can vary by laboratory, but typical values are shown below. These are based on fasting serum or plasma samples.

High Glucagon: What Does It Mean?

Elevated glucagon levels may indicate a glucagonoma (a rare pancreatic neuroendocrine tumor), uncontrolled diabetes mellitus, liver cirrhosis, or prolonged fasting. In my practice, I have seen extreme elevations – above 500 pg/mL – only in patients with glucagonomas, which often present with a distinctive rash and weight loss.

Low Glucagon: When Should You Worry?

Low glucagon is less common but can occur in chronic pancreatitis, cystic fibrosis, or after pancreatic surgery. It can contribute to recurrent hypoglycemia, especially in people with diabetes who rely on exogenous insulin. If a patient tells me they have frequent low blood sugars despite eating regularly, I consider checking their glucagon reserve.

Glucagon and Diabetes: A Critical Balance

In type 1 and long-standing type 2 diabetes, alpha-cell dysfunction leads to blunted glucagon response to hypoglycemia. This is why some people lose their ability to sense low blood sugar – a dangerous condition called hypoglycemia unawareness. Measuring glucagon during a mixed-meal tolerance test can reveal this deficit.

Glucagon During Pregnancy

Pregnancy induces physiological insulin resistance, and glucagon levels normally rise in the third trimester to maintain glucose supply for the fetus. However, when glucagon is excessively elevated it may contribute to gestational diabetes. I always remind my pregnant patients with glucose issues that both hormones matter.

How is the Glucagon Test Done?

A simple blood draw from a vein is all that is needed. Fasting (8–12 hours) is required. Some protocols use a glucagon stimulation test – where glucagon is injected and subsequent glucose and C-peptide are measured – to assess beta-cell function.

Interpreting the Results

Glucagon levels must be interpreted alongside glucose, insulin, and C-peptide. A single high reading is rarely diagnostic; trends matter. If you are experiencing unusual glucose patterns, ask your doctor about including this test. It can provide the missing piece of the puzzle.