GGT Blood Test (Gamma-Glutamyl Transferase)
The GGT blood test measures gamma-glutamyl transferase, an enzyme concentrated in the liver and the small ducts that carry bile. It is often ordered to add context to other liver-associated results rather than as a first-line test on its own.
About this test
GGT lives mostly along the liver's bile-handling pathways. That location gives it a particular niche in laboratory medicine: when clinicians see certain patterns in other liver-associated markers, GGT helps them think about whether the bile-duct side of the liver's plumbing is part of the story.
That responsiveness cuts both ways. GGT adds useful context, but it is rarely interpreted alone, because so many everyday exposures can move it. A clinician typically reads it alongside ALT, AST, alkaline phosphatase and the person's history.
Who might consider this test?
- Some people also follow it over time in conversations about alcohol and medication load.
- Interpretation belongs with a licensed clinician who knows your history.
Test details
| Quest code | 482 |
|---|---|
| Methodology | Spectrophotometry |
| Sample type | 1 mL serum |
| Collection | Quest patient service center |
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Additional details
GGT's niche: the bile-duct side of the liver
The liver makes bile and moves it through small ducts toward the digestive tract. GGT is concentrated along that pathway, so it is particularly associated with the duct side of liver activity. Clinicians often use it to add a dimension that ALT and AST — which speak more to liver cells themselves — do not cover.
A famously responsive enzyme
GGT reacts to many common exposures: alcohol is the best-known, and numerous prescription and over-the-counter medications can influence it too. This makes patterns and context essential; a single reading, without the story around it, says little.
How it pairs with alkaline phosphatase
Alkaline phosphatase is another enzyme associated with bile pathways, but it also comes from bone. When clinicians want to know which source is contributing, GGT often serves as the tie-breaker, since it shares the liver association but not the bone one.
Ordering a GGT test through Celio Health
GGT can be ordered on its own or alongside the liver-associated markers it is usually interpreted with, and a physician order is included with every purchase. Collection is a standard venous draw at a participating Quest Diagnostics patient service center, with results delivered securely as a PDF, typically within a few business days.
Because GGT earns its keep as a companion marker, many people order it together with ALT, AST and alkaline phosphatase so the full set arrives in one report.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What is GGT in a blood test?
GGT (gamma-glutamyl transferase) is an enzyme concentrated in the liver and its bile ducts. The test measures how much is circulating in blood.
Why would a clinician order GGT?
Usually to add context to other liver-associated results — particularly to explore the bile-duct side of the picture, or to help interpret an alkaline phosphatase result.
Can alcohol affect a GGT result?
Yes — GGT is well known for responding to alcohol, and to many common medications. That responsiveness is why it is always interpreted in context.
Do I need to fast before a GGT test?
GGT itself does not generally require fasting, though it is often drawn with panels that do. Follow the instructions on your requisition.
What does a GGT test cost without insurance?
$19. Celio Health's price is a flat cash price and insurance is never billed: the required physician's order is included.