8 Liver Function Tests for Fatty Liver Your Doctor Probably Never Ordered

You got an ultrasound, received a fatty liver diagnosis, and your doctor ordered only ALT, AST, and a CBC? If that sounds familiar, you are in the group of millions of Americans whose liver workup stopped halfway.

The problem is not lack of competence — it is a lack of updated protocols. Most annual checkups still operate with a lab panel from the 1990s, while science has already identified far more sensitive markers to evaluate what is actually happening inside your liver.

My name is Dr. Jean Carlos Barros de Oliveira, CRM 138479/SP, functional and integrative medicine physician for 16 years. In this article, I will list the 8 tests I consider essential for anyone diagnosed with fatty liver — and explain why each one changes the clinical approach.

For the full context on a natural approach to steatosis, start with our pillar: [Fatty Liver: Natural Treatment Based on Science](/en/fatty-liver-natural-treatment/).

Why the Standard Panel Is Insufficient

The classic “liver panel” includes ALT (SGPT), AST (SGOT), alkaline phosphatase, and bilirubin. These are useful tests, but they have a critical flaw: they only elevate when there is active cellular damage.

This means you can have a liver with 50% fat, rampant insulin resistance, and subclinical inflammation — and your liver enzymes can be completely normal.

A study published in Hepatology (2019) demonstrated that up to 50% of patients with biopsy-confirmed MASH had ALT within the laboratory reference range. In other words: relying solely on transaminases is like judging a house fire by only looking through the front window.

Functional medicine expands the field of view. We do not just want to know if the liver is damaged — we want to understand why, at what stage, and which metabolic pathways are compromised.

Test 1: HOMA-IR — The Thermometer of Insulin Resistance

HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) is calculated from fasting glucose and fasting insulin. Sounds simple — and it is. But most doctors do not order fasting insulin on a routine checkup.

This is a monumental oversight when it comes to fatty liver.

Insulin resistance is the number one metabolic driver of non-alcoholic hepatic steatosis. When cells become insulin-resistant, the pancreas compensates by producing more insulin. This excess insulin activates the enzyme de novo lipogenesis in the liver — literally turning sugar into liver fat.

Optimal values in functional medicine:

HOMA-IR below 1.5 (the lab typically considers “normal” up to 2.7 — but above 2.0 I already flag it as a concern)

Fasting insulin below 8 uIU/mL

If your HOMA-IR is elevated, steatosis treatment must include strategies to improve insulin sensitivity — and that completely changes the protocol.

Test 2: GGT (Gamma-Glutamyl Transferase) — Far More Than an Alcohol Marker

GGT is frequently associated with alcohol consumption, but it is actually one of the most sensitive markers of hepatic oxidative stress and cardiovascular risk.

> [WHAT THE SCIENCE SAYS]

> A meta-analysis published in the European Heart Journal (2020) with over 1.2 million participants demonstrated that elevated GGT is associated with a 26% increase in all-cause mortality risk, regardless of alcohol consumption. In the hepatic context, GGT reflects the depletion of glutathione — the liver's primary intracellular antioxidant.

Optimal values in functional medicine:

Men: below 25 U/L

Women: below 18 U/L

If GGT is elevated, it is not enough to treat the liver — you need to replenish glutathione (via NAC, glycine, alpha-lipoic acid) and investigate sources of oxidative stress.

Test 3: Serum Ferritin — The Forgotten Inflammatory Marker

Ferritin is not just an indicator of iron stores. In the context of steatosis, it functions as an acute phase protein — a marker of systemic inflammation.

Elevated ferritin in fatty liver patients can indicate:

Active hepatic inflammation (progression toward MASH)

Iron overload (which worsens oxidative damage)

Advanced metabolic syndrome

Optimal values in functional medicine:

Men: 50-150 ng/mL

Women: 30-100 ng/mL

Ferritin above 300 ng/mL in a patient with steatosis is a red flag that demands thorough investigation — including transferrin saturation and, potentially, genetic testing for hemochromatosis.

Test 4: High-Sensitivity CRP — The Temperature of Silent Inflammation

High-sensitivity C-reactive protein (hs-CRP) detects low-grade inflammation that conventional tests miss. In the hepatic context, it helps differentiate simple steatosis from steatosis with an active inflammatory component.

Optimal value: below 1.0 mg/L.

Values between 1.0 and 3.0 already indicate subclinical inflammation. Above 3.0, there is significant systemic inflammation accelerating both liver damage and cardiovascular risk simultaneously.

Test 5: Hepatic Elastography — What Ultrasound Does Not Show

Transient elastography (FibroScan) or MRI elastography measures the stiffness of liver tissue — a direct indicator of fibrosis.

This is perhaps the most undervalued test in standard clinical practice. While ultrasound shows that fat is present, elastography reveals whether that fat is already causing tissue scarring.

A patient with grade 2 steatosis and normal elastography has a completely different prognosis than one with grade 2 steatosis and F2 fibrosis. The treatment changes. The urgency changes. The protocol changes.

> [CLINICAL CASE]

> Robert, 52, Chicago, IL (online consultation). Ultrasound showed grade 2 steatosis, normal liver enzymes (ALT 32, AST 28). His previous doctor reassured him: “just a little fat.” In our functional evaluation, we ordered elastography: kPa 9.8 — F2 fibrosis. Additionally, HOMA-IR 5.1, ferritin 412, GGT 89. The “calm” liver on ultrasound was, in fact, actively fibrotic. With aggressive functional intervention — low-carb diet, supervised intermittent fasting, NAC + milk thistle + omega-3 + vitamin E supplementation, and therapeutic blood donation to reduce ferritin — in 10 months the elastography dropped to kPa 6.2 (F0-F1) and ferritin normalized at 148.

Test 6: Advanced Lipid Panel With Triglycerides and TG/HDL Ratio

The basic lipid panel (total cholesterol, LDL, HDL, triglycerides) is useful, but the triglyceride-to-HDL ratio is the indicator that matters most in steatosis.

This ratio directly reflects insulin resistance and hepatic lipogenesis.

Functional targets:

TG/HDL ratio below 2.0 (ideally below 1.5)

Triglycerides below 100 mg/dL

When the TG/HDL ratio exceeds 3.0, there is a greater than 80% probability that the patient has small dense LDL particles (pattern B) — the most atherogenic profile and the one most associated with steatosis.

Test 7: Homocysteine — The Link Between Methylation and Liver Health

Homocysteine is an amino acid whose metabolism depends on folate, B12, and B6. When elevated, it indicates a failure in the methylation cycle — a biochemical process critical to hepatic detoxification.

Optimal value: between 6 and 8 umol/L.

Elevated homocysteine in a patient with steatosis suggests that the liver has compromised methylation capacity — which worsens fat accumulation (methylation is required to produce phosphatidylcholine, essential for exporting triglycerides from the liver).

Test 8: Zonulin and Fecal Calprotectin — The Window to the Gut-Liver Axis

These two tests evaluate, respectively, intestinal permeability (zonulin) and intestinal inflammation (fecal calprotectin).

Why do they matter for the liver? Because everything that passes through a leaky gut goes straight to the liver via the portal vein. Bacterial endotoxins (LPS), bacterial fragments, and inflammatory mediators reach the liver and activate Kupffer cells — triggering an inflammatory cascade that transforms simple steatosis into steatohepatitis.

Understanding this mechanism is so important that we dedicated an entire article to the topic: [The Gut-Liver Axis: The Connection That May Be Sabotaging Your Liver Health](/en/gut-liver-axis/).

Reference values:

Zonulin: below 48 ng/mL

Fecal calprotectin: below 50 ug/g

How to Build Your Complete Panel

The best approach is to bring this list to your doctor and request the tests together. If possible, find a functional or integrative medicine practitioner who already works with this expanded panel.

Essential panel summary:

| Test | What It Evaluates | Functional Target |

|——|——————-|——————-|

| HOMA-IR | Insulin resistance | < 1.5 |

| GGT | Oxidative stress | M: < 25 / F: < 18 U/L |

| Ferritin | Inflammation / iron | M: 50-150 / F: 30-100 ng/mL |

| hs-CRP | Silent inflammation | < 1.0 mg/L |

| Elastography | Hepatic fibrosis | < 7.0 kPa |

| TG/HDL | Hepatic lipogenesis | < 2.0 |

| Homocysteine | Methylation | 6-8 umol/L |

| Zonulin | Intestinal permeability | < 48 ng/mL |

FAQ — Liver Function Tests for Fatty Liver

1. My doctor said normal ALT and AST mean my liver is fine. Is that true?

Not necessarily. Up to 50% of patients with biopsy-confirmed steatohepatitis have normal transaminases. ALT and AST are markers of cellular damage, not of fat or fibrosis.

2. Do I need a liver biopsy?

In most cases, no. The combination of elastography + comprehensive lab panel + imaging provides sufficient information to guide treatment. Biopsy is reserved for cases with inconclusive diagnosis.

3. Does insurance cover these tests?

HOMA-IR, GGT, ferritin, hs-CRP, homocysteine, and the lipid panel are covered by most insurance plans with a physician's order. Elastography and zonulin may require prior authorization or clinical justification.

4. How often should I repeat these tests?

I recommend a complete reassessment every 3 to 4 months at the start of treatment and every 6 months after stabilization.

5. Can I order these tests on my own?

Some direct-to-consumer labs offer these panels, but the ideal approach is to have a practitioner who can interpret the results together — isolated values mean little. The clinical context is everything.

Want to know which tests to prioritize for your case and how to interpret them?

Access Dr. Jean Carlos's complete guide:

[drjeancarlosmd.com/en/fatty-liver-natural-treatment/](https://drjeancarlosmd.com/en/fatty-liver-natural-treatment/)