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How blood-based liver tests work
No blood test can watch your liver working. Instead, a blood panel picks up the traces your liver leaves behind in your bloodstream: substances that leak out when cells are damaged, proteins the liver manufactures and substances it is supposed to clear away. Read together, those traces produce a useful picture of what may be happening inside the liver.
Enzymes
ALT, AST and GGT can rise when liver cells are stressed or damaged.
Proteins
Albumin, total protein and globulin help show whether the liver is maintaining its synthetic function.
Clearance
Bilirubin can show whether the liver is processing waste and whether bile is draining normally.
1. Enzymes that leak out when liver cells are stressed
Your liver cells contain enzymes that perform metabolic work inside the cell. They are not supposed to circulate in significant quantities. When hepatocytes are inflamed, damaged or dying, those enzymes can spill into the bloodstream.
- ALT (alanine aminotransferase) is the most liver-specific of the group. It lives mainly in the liver, so a raised ALT points relatively directly to hepatic stress.
- AST (aspartate aminotransferase) does similar work but also appears in muscle, heart, kidney and red blood cells. That is why AST is not interpreted alone. A hard workout or muscle injury can increase it without the liver being involved.
- GGT (gamma-glutamyl transferase) sits in liver cells and the cells lining the bile ducts. It is notably sensitive to alcohol, bile-flow obstruction and oxidative stress, and it can rise before ALT.
An important caveat: Enzyme levels reflect ongoing injury. A badly scarred liver that is no longer actively inflamed can produce normal enzyme readings, which is one reason a single in-range result is not a complete assessment of liver health.
2. Proteins the liver manufactures
Enzymes tell you about damage. The proteins your liver builds tell you about capacity, or whether the liver is still doing its job.
Albumin is the main marker. The liver is the only organ that makes it, and it circulates for roughly three weeks, so albumin reflects sustained synthetic function.
Total protein and globulin add context, while the albumin/globulin ratio compares them. Because albumin turns over slowly, these markers tend to shift only in longer-standing liver disease. They add clinical depth but are less useful for tracking a recent lifestyle change.
3. Substances the liver is supposed to clear
Bilirubin is the yellow pigment left over when old red blood cells break down. A healthy liver conjugates it and sends it out through bile. When it backs up in the blood, either the liver is not processing it or bile is not draining. At high enough levels, it produces the yellowing of the skin and eyes associated with jaundice.
Calculated values and metabolic context
Some of the most useful outputs are not measured directly. They are derived from other markers.
- The AST:ALT ratio reads the relationship between the two enzymes rather than either number alone. When AST is meaningfully higher than ALT, the pattern can suggest alcohol-related stress rather than metabolic causes.
- The FIB-4 Index combines age, AST, ALT and platelet count to estimate the risk of advanced fibrosis.
- HbA1c reflects average blood sugar over approximately two to three months.
- hsCRP measures systemic inflammation.
- Visceral fat is the fat stored around the internal organs.
Metabolic dysfunction is now a leading driver of chronic liver disease, so metabolic markers can help reveal why an enzyme is elevated rather than simply showing that it is elevated.
Liver tests from Choose Health vs. Quest Diagnostics
Liver testing comparison: Choose Health Liver Function Test and Comprehensive Liver Function Test vs. Quest Liver Function Test Panel and Quest Advanced Fatty Liver Disease Test Panel. Verified against provider websites in August 2026.
| Feature | Choose Health Liver Function |
Choose Health Comprehensive |
Quest Liver Function |
Quest Advanced Fatty Liver |
|---|---|---|---|---|
| Best for | At-home retesting | Fullest at-home picture | Full clinical liver chemistry | Fibrosis risk assessment |
| Listed price | $90 | $165 | $119 | $89 |
| Promotional price | $75 with LIVER15 | $135 with LIVER30 | Varies | Varies |
| Additional fees | None | None | +$6 physician service fee | +$6 physician service fee |
| Real total | $75–$90 | $135–$165 | $125 | $95 |
| Collection method | Finger-prick at home | Finger-prick at home | In person at a Quest patient service center | In person at a Quest patient service center |
| At-home collection | Included | Included | Quest Mobile, +$79 ($204 total) | Quest Mobile, +$79 ($174 total) |
| Appointment required | No | No | Yes | Yes |
| Core liver enzymes | ALT, AST, GGT | ALT, AST, GGT | ALT, AST, GGT, ALP | ALT, AST |
| AST:ALT ratio reported | Yes | Yes | No | No |
| Bilirubin | No | Total | Total, direct, indirect | No |
| Albumin | No | Yes | Yes | No |
| Fibrosis scoring | No | No | FIB-4 Index | FIB-4 Index + ELF reflex |
| Metabolic context | HbA1c | HbA1c, fasting glucose, fasting insulin | No | No |
| Cardiovascular | No | HDL, LDL, triglycerides, ApoA, ApoB | No | No |
| Iron status | No | Ferritin, iron, UIBC, transferrin saturation | No | No |
| Total markers | 7 | 20+ | 13 | 4 + ELF reflex |
| Lab accreditation | CAP and CLIA accredited | CAP and CLIA accredited | CLIA certified | CLIA certified |
| Turnaround | Approx. 3–4 days after the lab receives the sample | Approx. 3–4 days after the lab receives the sample | 2–3 business days after collection | 2–3 business days after collection |
| Provider support | Optional telehealth consult | Optional telehealth consult | Included at no extra cost | Included at no extra cost |
| HSA/FSA | Accepted | Accepted | Accepted | Accepted |
| Insurance | Not billed | Not billed | Not billed or reimbursable | Not billed or reimbursable |
| Availability limits | Not stated | Not stated | Not in AZ, HI or PR | Not in AZ, HI or PR |
Choose Health Liver Function Test
Markers tested: ALT, AST, AST:ALT ratio, GGT, average blood sugar (HbA1c), inflammation (hsCRP) and a visceral fat assessment.
Collection method: Finger-prick at-home liver testing. Collect four to five drops of blood and return your sample in a prepaid envelope.
Lab accreditation: CAP and CLIA accredited laboratories.
Price: $90 for a one-time test with no added fees, or $75 with code LIVER15. HSA/FSA accepted, free shipping and a 30-day money-back guarantee on your first purchase.
Results delivery: A HIPAA-compliant dashboard with insights and recommendations, plus the option to speak with a telehealth practitioner.
What it covers well: All three core liver enzymes plus the AST:ALT ratio, which adds context about the pattern of an elevation rather than only its size. The metabolic and inflammatory markers are the key differentiators from Quest. HbA1c, hsCRP and a visceral fat assessment add insight into insulin resistance and inflammation, factors that often sit underneath metabolic liver disease. Quest’s liver panels do not include these three measures.
The trade-off: No bilirubin, ALP, albumin, protein markers or fibrosis scoring. This is a metabolic-leaning liver panel, not a complete hepatic panel.
Choose Health Comprehensive Liver Function Test
Markers tested: Albumin, AST, ALT, the AST:ALT ratio, GGT and total bilirubin for liver health; HDL, LDL, triglycerides, ApoA and ApoB for cardiovascular health; fasting glucose, fasting insulin and HbA1c for metabolic health; and ferritin, iron, UIBC and transferrin saturation for iron status.
Collection method: The same at-home finger-prick as the standard test. Collect four to five drops of blood, then return your sample in the prepaid envelope with no appointment required.
Lab accreditation: CAP and CLIA accredited laboratories.
Price: $165, or $135 with code LIVER30. One-time purchase with no membership required. HSA/FSA accepted, free shipping both ways and a 30-day money-back guarantee on your first purchase.
Results delivery: A HIPAA-compliant dashboard with physician-reviewed results, insights and recommendations for markers outside the optimal range.
What it covers well: This is the panel that changes the shape of the Quest comparison. Adding albumin and total bilirubin closes part of the clinical gap by including a marker of synthetic function and one of clearance capacity alongside the liver enzymes.
The broader story is what surrounds the liver markers. Fasting insulin can signal insulin resistance before fasting glucose or HbA1c moves, and it appears in neither Quest liver panel. The iron panel is another meaningful differentiator. Transferrin saturation and ferritin are standard screening markers for iron overload, and hereditary hemochromatosis is a recognized cause of liver damage. ApoB and lipid markers round out the cardiometabolic picture associated with fatty liver disease.
The trade-off: There is still no FIB-4 fibrosis score. That calculation requires a platelet count, which is not available through this finger-prick collection.
Quest Liver Function Test Panel
Markers tested: Total protein, albumin, globulin, albumin/globulin ratio, total bilirubin, direct bilirubin, indirect bilirubin, ALP, AST, ALT, GGT, platelet count and the FIB-4 Index.
Collection method: In person at a Quest patient service center. Quest Mobile in-home collection is available in some areas for an additional $79.
Lab accreditation: CLIA certified laboratories.
Price: $119 plus a $6 physician service fee, or $125 total. With Quest Mobile in-home collection, the total is $204. HSA/FSA accepted. Quest does not bill insurance, and these purchases cannot be submitted for reimbursement.
Results delivery: A secure emailed link and the MyQuest portal. You may receive a call if results fall outside expected ranges.
What it covers well: This resembles a panel a physician might order, with GGT and a fibrosis calculation added. Bilirubin fractions and ALP cover bile flow. Albumin and total protein reflect synthetic function. The FIB-4 Index, calculated from age, AST, ALT and platelet count, is a validated score that estimates the risk of advanced liver fibrosis.
The trade-off: You have to visit a lab location. At-home collection is not included, and adding it costs $79. The panel also contains no metabolic or inflammatory markers, so it shows liver chemistry without adding much context about why an enzyme may be elevated.
Quest Advanced Fatty Liver Disease Test Panel
Markers tested: ALT, AST, platelet count and the FIB-4 Index, with reflex testing to an ELF (Enhanced Liver Fibrosis) score.
Price: $89 plus the $6 physician service fee, or $95 total.
What it covers well: It is designed to answer one specific question: whether you may be at risk of advanced fibrosis. Quest notes that this test may be less accurate for adults under 35 or over 65.
The trade-off: As a general liver check, it is limited. There is no GGT, ALP, bilirubin, protein or metabolic marker. If you are completing a first liver check rather than specifically assessing fibrosis risk, this is not a broad liver panel.
Side-by-side marker comparison
| Marker | Choose Health Liver Function |
Choose Health Comprehensive |
Quest Liver Function |
Quest Advanced Fatty Liver |
|---|---|---|---|---|
| ALT | Yes | Yes | Yes | Yes |
| AST | Yes | Yes | Yes | Yes |
| GGT | Yes | Yes | Yes | No |
| ALP | No | No | Yes | No |
| AST:ALT ratio | Yes | Yes | No | No |
| Total bilirubin | No | Yes | Yes | No |
| Direct / indirect bilirubin | No | No | Yes | No |
| Total protein | No | No | Yes | No |
| Albumin | No | Yes | Yes | No |
| Globulin / A:G ratio | No | No | Yes | No |
| Platelet count | No | No | Yes | Yes |
| FIB-4 Index | No | No | Yes | Yes |
| ELF score | No | No | No | Reflex |
| HbA1c | Yes | Yes | No | No |
| Fasting glucose | No | Yes | No | No |
| Fasting insulin | No | Yes | No | No |
| hsCRP | Yes | Not listed | No | No |
| Visceral fat | Yes | Not listed | No | No |
| HDL, LDL, triglycerides | No | Yes | No | No |
| ApoA, ApoB | No | Yes | No | No |
| Ferritin, iron, UIBC, TSAT | No | Yes | No | No |
| Real total price | $75–$90 | $135–$165 | $125 | $95 |
| At-home collection | Included | Included | +$79 | +$79 |
Methodology: Prices, panel contents, fees and availability change frequently and may vary by state. Quest pricing reflects list price plus the physician service fee displayed in August 2026. Information was verified directly against choosehealth.io and questhealth.com in August 2026. Confirm current details before purchasing.
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