Quest Diagnostics Results Explained: What Every Number Means

How Quest Diagnostics Reports Are Structured

Your Quest report comes through MyQuest (their patient portal) or as a PDF from your doctor. It typically shows three columns: the test name, your result, and the reference range. Results flagged with an H (high) or L (low) sit outside the standard reference range — but this doesn't automatically mean something is wrong. Reference ranges are statistical averages, not optimal targets.

Most Quest reports group results into panels: a Comprehensive Metabolic Panel (CMP), a Complete Blood Count (CBC), a lipid panel, and any add-on tests your doctor ordered. Each panel tells a different story about your health.

The Comprehensive Metabolic Panel (CMP)

The CMP is 14 tests in one. It covers your blood sugar, kidney function, liver function, and electrolyte balance. Here's what each section means:

Blood sugar (Glucose): Normal fasting range is 70–99 mg/dL. Between 100–125 mg/dL is considered pre-diabetes by US guidelines. Above 126 mg/dL on two separate tests is diagnostic for diabetes. This is one of the most important numbers on your report.

Kidney markers (BUN and Creatinine): Blood Urea Nitrogen (BUN) and Creatinine measure waste products your kidneys filter out. Quest also calculates your eGFR (estimated Glomerular Filtration Rate) — a score above 60 is generally normal; below 60 warrants follow-up with your doctor.

Liver markers (ALT, AST, ALP, Bilirubin): These four values indicate how well your liver is functioning. Mildly elevated ALT and AST (under twice the upper limit) are common and often related to fatty liver disease, alcohol, or recent intense exercise. Persistently high values need investigation.

Electrolytes (Sodium, Potassium, CO2, Chloride): These rarely flag abnormal unless you have a specific condition. Sodium and potassium are the ones most worth watching — both affect heart rhythm and muscle function.

Proteins (Total Protein, Albumin): Albumin is a key protein made by the liver. Low albumin can indicate poor nutrition, liver disease, or kidney disease. It's one of the cleaner markers of overall metabolic health.

The Lipid Panel

The lipid panel measures fats in your blood. Quest reports four values: Total Cholesterol, LDL ("bad" cholesterol), HDL ("good" cholesterol), and Triglycerides. Understanding these together matters more than any single number.

Total Cholesterol: Quest flags above 200 mg/dL as borderline high. In isolation, total cholesterol is less useful than the breakdown into LDL and HDL.

LDL Cholesterol: The US standard optimal target is under 100 mg/dL. If you have cardiovascular risk factors, your doctor may aim for under 70 mg/dL. Quest's reference range shows under 130 mg/dL as normal — but most cardiologists consider under 100 mg/dL optimal.

HDL Cholesterol: This is the one you want high. Under 40 mg/dL in men and under 50 mg/dL in women increases cardiovascular risk. Above 60 mg/dL is protective.

Triglycerides: Quest's normal range is under 150 mg/dL. Under 100 mg/dL is optimal. Triglycerides are heavily influenced by diet — they spike after eating carbohydrates and alcohol, which is why this test requires fasting.

The Complete Blood Count (CBC)

The CBC measures the cells in your blood. It's divided into red blood cells, white blood cells, and platelets.

Red blood cell markers (RBC, Hemoglobin, Hematocrit): These three values move together and measure your blood's oxygen-carrying capacity. Low hemoglobin is the classic marker of anemia — in the US, below 13.5 g/dL in men and below 12 g/dL in women is flagged low. Iron deficiency is the most common cause in women of reproductive age.

White blood cells (WBC): WBC counts rise during infection and inflammation. Quest's normal range is 4.5–11.0 thousand/μL. A chronically elevated WBC warrants investigation even if it seems minor — persistent low-grade elevation can indicate inflammation, autoimmune conditions, or in rare cases, something more serious.

Platelets: Normal range is 150–400 thousand/μL. Platelets are needed for clotting. Very low counts (below 50) require urgent attention.

What the H and L Flags Actually Mean

Quest flags a result as H or L when it falls outside the reference range — a statistical range calculated from a population of tested individuals. Roughly 5% of perfectly healthy people will have a result outside the reference range on any given test purely by chance.

A single flagged result, especially a borderline one, is rarely cause for alarm on its own. What matters more is the pattern across multiple markers, your symptoms, your history, and the trend over time. Always discuss flagged results with your doctor before drawing conclusions.

The Difference Between 'Normal' and 'Optimal'

Quest's reference ranges are designed to identify disease, not to define excellent health. A result can be within the reference range and still be far from optimal. LDL at 129 mg/dL is technically "normal" by Quest's range — but research consistently shows that LDL under 70 mg/dL is associated with the lowest cardiovascular risk.

This gap between normal and optimal is exactly why reading your report against research-backed optimal ranges, not just lab reference ranges, gives you a more accurate picture of where you stand.

How to Get the Most from Your Quest Results

Rather than looking at each number in isolation, the most useful approach is to look at clusters: how do your liver markers look together? Do your kidney markers tell a consistent story? Is your metabolic picture (glucose, triglycerides, HDL) pointing in a clear direction?

Uploading your Quest PDF to Clariti takes 30 seconds and gives you a scored breakdown by health domain — cardiovascular, metabolic, kidney, liver, blood, and inflammatory health — with plain-English explanations of what each score means and what moves it.