Your Blood Test Results, Explained in Plain English

You open your patient portal to a page full of abbreviations, numbers, and red flags. Your cholesterol is marked "H," your glucose is borderline, and something called MCV is low. Nobody called you, so you do what millions of Americans do: you search the internet and worry.

Here is the reassuring truth first. A flagged result is not a diagnosis. It is a prompt. Lab reports compare your numbers to a reference range covering about 95 percent of healthy people tested by that lab, so about 1 in 20 healthy results falls outside it. What matters is how far outside it you are, whether the pattern fits together, and how the number changes over time.

Ranges vary by lab, age, and sex, so the numbers below are typical adult ranges, not a substitute for your own report. Use this guide to understand your doctor, not to replace them.

The complete blood count (CBC)

The CBC counts the cells in your blood.

Red blood cells, hemoglobin, and hematocrit. Hemoglobin carries oxygen in red blood cells. A typical range is about 14 to 18 grams per deciliter for men and 12 to 16 for women. Hematocrit runs roughly 41 to 50 percent for men and 36 to 44 percent for women. Low values can point to anemia; high values can reflect dehydration, smoking, or lung disease.

MCV, or mean corpuscular volume. This is the average size of your red blood cells, usually 80 to 100 femtoliters. Small cells often suggest iron deficiency; large cells can suggest low vitamin B12, heavy alcohol use, or certain medications.

White blood cells (WBC). These fight infection, typically 4,500 to 11,000 cells per microliter. A high count often means infection or inflammation; a low count can follow a viral illness, certain medications, or a bone marrow problem.

Platelets. These help blood clot, usually 150,000 to 400,000 per microliter. Low platelets can raise bruising and bleeding risk; high platelets can reflect inflammation or iron deficiency.

The metabolic panel: kidneys, salts, and sugar

A metabolic panel measures chemicals that reflect kidney function, fluid balance, and blood sugar.

Glucose. A fasting glucose of 70 to 99 milligrams per deciliter is normal. From 100 to 125 is prediabetes, and 126 or higher, confirmed on a repeat test, is diabetes. The CDC estimates about 38.4 million Americans have diabetes and roughly 97.6 million adults have prediabetes, so a borderline result is common and often reversible with weight loss, activity, and diet changes.

Sodium and potassium. Sodium usually runs 135 to 145 milliequivalents per liter, and potassium 3.5 to 5.0. Potassium is watched most closely, because very high or very low levels can affect heart rhythm. Mild shifts are often caused by dehydration, vomiting, diarrhea, or diuretics.

Calcium. The typical range is about 8.5 to 10.5 milligrams per deciliter. High calcium can point to an overactive parathyroid gland; low calcium can reflect low vitamin D or kidney disease.

Kidney numbers: creatinine, BUN, and eGFR. Creatinine, a waste product from muscle, usually runs about 0.7 to 1.3 milligrams per deciliter for men and 0.6 to 1.1 for women. Doctors convert it into an estimated glomerular filtration rate, or eGFR. An eGFR of 60 or higher is generally normal, while a persistently low eGFR can signal chronic kidney disease. BUN, or blood urea nitrogen, typically runs 7 to 20 milligrams per deciliter; a high BUN with a normal creatinine often just means you were dehydrated.

Liver numbers: ALT and AST. These enzymes leak into blood when liver cells are irritated: ALT usually 7 to 55 units per liter, AST 8 to 48. Mild elevations are common, often tied to fatty liver disease, alcohol, or acetaminophen.

The cholesterol panel

A lipid panel measures fats in your blood and is one of the strongest heart-risk predictors you can change.

Total cholesterol. Below 200 milligrams per deciliter is considered desirable, 200 to 239 is borderline high, and 240 or above is high. The breakdown matters more.

LDL, the "bad" cholesterol. Below 100 is optimal, 130 to 159 is borderline high, and 190 or above is high. LDL drives plaque buildup in arteries and is the number doctors most want to lower.

HDL, the "good" cholesterol. Higher is better: 60 or above is considered protective. Below 40 for men and below 50 for women is low. Exercise, quitting smoking, and losing excess weight tend to raise it modestly.

Triglycerides. Below 150 is normal, 150 to 199 is borderline high, and 500 or above is very high and can inflame the pancreas. Triglycerides respond quickly to cutting back on added sugar and alcohol, and they run higher after eating, so fasting matters.

A1C: your three-month blood sugar average

If glucose is a snapshot, A1C is a three-month exposure, measuring the percentage of hemoglobin coated with sugar.

Below 5.7 percent is normal, 5.7 to 6.4 percent is prediabetes, and 6.5 percent or higher, confirmed by a repeat test, is diabetes. A1C is less affected by one heavy meal than a single glucose reading. Anemia and kidney disease can distort it.

Why a healthy person gets an abnormal result

Before you panic over a flag, run through the usual suspects. Dehydration can raise hemoglobin, BUN, and sodium. A hard workout can raise muscle and liver enzymes. Alcohol the night before can raise triglycerides and liver numbers. Statins, diuretics, and steroids predictably shift results, and a non-fasting sample can skew glucose and triglycerides.

A trend across several tests tells a far more reliable story than any single number.

When to call your doctor promptly

Most flags can wait for your next appointment. Seek prompt advice if a result is dramatically out of range, such as a very low hemoglobin, a potassium well above 5.5 or below 3.0, or a glucose above 300 milligrams per deciliter, especially with symptoms. Also call if several related numbers move together: low hemoglobin plus low iron, or high glucose plus high A1C. Patterns point to a cause; isolated blips usually do not.

Seek emergency care for chest pain, shortness of breath, confusion, severe weakness, or bleeding along with an abnormal result.

How to get the most from your next lab visit

Follow fasting instructions exactly: usually nothing but water for 8 to 12 hours before a glucose or lipid test. Bring a list of every medication and supplement you take, because many shift lab values. Then ask: Is this new or trending? Does it need a repeat test, a lifestyle change, or treatment? And when should we recheck it?

Keep your own record: a simple note of your key numbers each year lets you spot a slow drift early.

The bottom line

Your lab report is a dashboard, not a verdict. Most flags are mild, many are temporary, and nearly all are more informative in context: your symptoms, your medications, and your previous results. The goal is catching the few numbers that matter early, while you still have time to change them.

This article is for general information only and is not medical advice. Talk to your doctor about what your lab results mean for you.