When laboratory testing reveals elevated transaminases (ALT or AST), medical documentation requires specific diagnostic coding to establish insurance necessity. The primary clinical code is ICD-10 Code: R74.01 (Elevation of levels of liver transaminase levels). If fatty liver disease is confirmed, coding transitions to K76.0 (Metabolic Fatty Liver / MASLD) or K75.81 (NASH / MASH). Following an elevated result, clinical guidelines mandate a stepwise workup ruling out viral hepatitis, hemochromatosis, and medication toxicity.
When an annual physical or routine metabolic panel returns with an elevated ALT or AST, the laboratory and your physician must attach an official diagnostic code to justify insurance coverage for subsequent investigations.
For both patients and healthcare providers, selecting the correct ICD-10-CM code is essential to ensure that follow-up imaging (such as an abdominal ultrasound or FibroScan) and secondary viral blood tests are approved without out-of-pocket claim denials.
What are the official ICD-10 codes for elevated liver function tests, how do diagnostic codes transition as a cause is confirmed, and what is the standard stepwise clinical workup?
Official ICD-10 Diagnostic Codes for Elevated Liver Enzymes#
Depending on whether the elevation is an isolated laboratory finding or tied to a confirmed diagnosis, physicians use the following ICD-10-CM codes:
| ICD-10 Code | Official Diagnostic Description | Clinical Application & Usage |
|---|---|---|
| R74.01 | Elevation of levels of liver transaminase levels | The Primary Symptom Code: Used when a routine blood test reveals elevated ALT and/or AST before a definitive diagnosis is established. |
| R74.8 | Abnormal levels of other serum enzymes | Used for elevated Alkaline Phosphatase (ALP), GGT, or LDH when transaminases are normal. |
| R74.9 | Abnormal serum enzyme level, unspecified | Non-specific code used when general enzyme elevation is documented without subtype breakdown. |
| K76.0 | Fatty (change of) liver, not elsewhere classified | Used once imaging (ultrasound, CT, MRI) confirms Metabolic Fatty Liver Disease (MASLD). |
| K75.81 | Non-alcoholic steatohepatitis (NASH / MASH) | Used when clinical or histological evidence confirms active inflammatory steatohepatitis. |
| K70.10 | Alcoholic hepatitis without ascites | Used when liver enzyme elevation (AST > ALT ratio > 2.0) is driven by chronic alcohol consumption. |
| B18.2 | Chronic viral hepatitis C | Used when transaminitis is linked to confirmed Hepatitis C viral infection. |
| B18.1 | Chronic viral hepatitis B without delta-agent | Used when transaminitis is linked to confirmed Hepatitis B viral infection. |
The Stepwise Clinical Diagnostic Workup Algorithm#
When a patient presents with an isolated R74.01 (Elevated Transaminases), American College of Gastroenterology (ACG) guidelines recommend a 4-phase diagnostic algorithm:
[Phase 1: History & Medication Reconciliation]
- Discontinue hepatotoxic herbal supplements (kava, green tea extract, high-dose niacin)
- Evaluate alcohol consumption & prescription medications (statins, NSAIDs, acetaminophen)
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[Phase 2: Viral & Metabolic Blood Panels]
- Hepatitis B Surface Antigen (HBsAg) & Hepatitis C Antibody (with reflex RNA)
- Fasting Iron & Ferritin with Transferrin Saturation (Screen for Hemochromatosis)
- HbA1c & Fasting Lipid Panel (Screen for Metabolic MASLD)
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[Phase 3: Autoimmune & Rare Genetic Screening (If Phase 2 is Negative)]
- Antinuclear Antibodies (ANA) & Anti-Smooth Muscle Antibodies (ASMA) for Autoimmune Hepatitis
- Ceruloplasmin (Wilson's Disease) & Alpha-1 Antitrypsin Phenotype
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[Phase 4: Non-Invasive Liver Imaging]
- Right Upper Quadrant (RUQ) Abdominal Ultrasound (identifies steatosis, gallstones, biliary dilation)
- Transient Elastography (FibroScan) to quantify liver stiffness (kPa)
Why Codes Transition from "R" to "K" Codes#
In medical coding architecture:
- "R" Codes (Symptoms & Abnormal Findings): Code R74.01 is a preliminary finding code. It indicates that the laboratory found elevated enzymes, but does not identify the root cause.
- "K" Codes (Digestive System Diseases): Once an abdominal ultrasound confirms hepatic steatosis, your physician updates your chart to K76.0 (MASLD). This establishes permanent medical necessity for long-term metabolic monitoring and FibroScan surveillance.
If elevated transaminases are accompanied by jaundice (yellowing of the skin or eyes), dark tea-colored urine, clay-colored stools, or confusion (hepatic encephalopathy), immediate emergency department evaluation is required.
To learn about CPT procedure codes for routine blood work, read Medical Billing Codes for Blood Tests: CPT & ICD-10 Guide.
Track Your Health & Liver Diagnostic Records with Meridian#
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Take control of your liver health and medical privacy today. Download Meridian on the App Store and keep your diagnostic records organized, private, and secure.