What HDL, LDL, TSH and CBC actually mean

A plain-language glossary · Updated June 2026

Understanding lab results

How to read any lab abbreviation

Most blood tests are organized into panels — groups of related markers ordered together. The lipid panel looks at fats in your blood, the thyroid panel at thyroid signaling, the complete blood count at your blood cells, and the metabolic panel at things like glucose and kidney function. Once you know which panel a marker belongs to, the abbreviation gets a lot less intimidating.

Two things sit next to almost every result:

• A value — the measured number, in some unit (mg/dL, mmol/L, mIU/L, and so on).
• A reference range — the band of values the lab considers typical for most people tested with their equipment. It is a statistical guide, not a verdict, and it differs from one lab to the next.

A result inside the range is generally described as expected; one outside it is flagged for a closer look. What that look concludes is a conversation for you and your clinician.

The lipid panel: HDL, LDL, and friends

The lipid panel measures fats (lipids) circulating in your blood. It's one of the most common reasons people stare at abbreviations.

• HDL — high-density lipoprotein. Often called the "helpful" cholesterol because these particles carry cholesterol away from tissues and back toward the liver. On most reports, higher HDL is viewed favorably.
• LDL — low-density lipoprotein. The type that can contribute to buildup in artery walls over time, which is why it gets so much attention. It is frequently calculated rather than measured directly.
• Total cholesterol — the overall amount of cholesterol in your blood, combining the different types.
• Triglycerides — a separate kind of fat used for energy storage; often reported in the same panel.

These markers are tested together because cardiovascular health is about the balance between them, not any one number alone. Two people with the same total cholesterol can have very different pictures depending on their HDL, LDL, and other factors. That balance is exactly the kind of thing a clinician weighs.

The thyroid panel: TSH and beyond

Your thyroid is a small gland in your neck that helps set your metabolism. Thyroid markers look at the signaling loop that controls it.

• TSH — thyroid-stimulating hormone. Slightly counterintuitively, TSH is made by the pituitary gland, not the thyroid. It's the message telling the thyroid how hard to work, which makes it a sensitive first look at thyroid function. Because of the feedback loop, TSH and actual thyroid hormone levels often move in opposite directions.
• Free T4 (thyroxine) and Free T3 (triiodothyronine) — the thyroid hormones themselves, sometimes added when TSH alone raises questions.

TSH is usually ordered first because it's so responsive. But it is read in context — a single TSH outside the range can have many explanations, including timing, recent illness, or normal individual variation, which is why follow-up markers exist.

The complete blood count (CBC)

The CBC is one of the most-ordered tests in medicine. It counts and characterizes the cells in your blood and is used for everything from routine checkups to following up on symptoms.

• RBC — red blood cell count, the cells that carry oxygen.
• Hgb (hemoglobin) and Hct (hematocrit) — measures of how much oxygen-carrying capacity your blood has and the proportion of your blood made up of red cells.
• WBC — white blood cell count, part of your immune system. A differential breaks this into types like neutrophils and lymphocytes.
• Platelets (PLT) — the cell fragments involved in clotting.
• MCV, MCH, MCHC — "indices" that describe the size and content of your red cells, which add nuance to the basic counts.

Because the CBC reports so many values at once, it's normal for one or two to sit slightly outside a range without that meaning anything on its own. Patterns across the whole panel, and how they compare to your past results, are what a clinician actually reads.

The metabolic panel and other common markers

A basic or comprehensive metabolic panel (BMP/CMP) checks how several core systems are running.

• Glucose — blood sugar at the time of the draw; fasting status changes how it's interpreted.
• Creatinine and BUN (blood urea nitrogen) — waste products used to gauge how the kidneys are filtering.
• eGFR — an estimate of kidney filtration rate, often calculated from creatinine.
• Electrolytes — sodium (Na), potassium (K), chloride (Cl), and others that keep fluid and nerve function balanced.
• ALT, AST, ALP, bilirubin — liver-related markers grouped in the comprehensive version.

You'll also run into standalone tests like HbA1c (a three-month average of blood sugar), vitamin D, and ferritin (an iron-storage marker). Each lives in its own context, and units matter enormously — the same marker can read as a wildly different number depending on whether it's reported in mg/dL or mmol/L.

Why ranges are guides, not grades

It's worth repeating, because it's the single most misread part of a lab report: a reference range is a statistical band, built from a population the lab tested on its own equipment. Ranges differ between labs, shift with age and sex, and don't account for your personal baseline. A value just outside a range is common and frequently unremarkable; a value inside one isn't a guarantee of anything either.

This is also why a single snapshot tells you so little. The useful signal is usually the trend — how your HDL, TSH, or hemoglobin moves across years — which is hard to see when each result lives in a separate PDF or portal. For more on putting numbers in context, see our guide on how to read your blood test results, or browse more lab-results articles.

What none of this can do is tell you what your specific value means. That genuinely depends on your history, symptoms, and other tests — and it's exactly the judgment a clinician is trained for. Use this glossary to understand the vocabulary, then bring your questions to someone who can interpret the numbers with you.

Frequently asked questions

What do lab result abbreviations mean?

Most abbreviations on a blood test are short names for specific markers grouped into panels. HDL and LDL are cholesterol types in a lipid panel, TSH is a thyroid hormone marker, and CBC is the complete blood count that measures red cells, white cells, and platelets. Each measures one part of how your body is working.

Is HDL or LDL the good cholesterol?

HDL is often called the helpful cholesterol because it carries cholesterol away from tissues, while LDL is the type that can build up in artery walls. Both are normal parts of your blood, and what any single number means depends on the lab, the units, and your overall health picture, which a clinician interprets together.

What does TSH measure?

TSH stands for thyroid-stimulating hormone. It is the signal your pituitary gland sends to tell the thyroid how much hormone to make, so it is commonly used as a first look at thyroid function. It does not diagnose a condition on its own and is read alongside other thyroid markers when needed.

What is a CBC blood test?

CBC stands for complete blood count. It is one of the most common blood tests and reports the numbers and characteristics of your red blood cells, white blood cells, and platelets. It gives a broad snapshot used for routine checks and follow-up rather than a single specific answer.