How to read your blood test results

The two panels behind most routine blood work

When a doctor says “we will run some blood work,” they usually mean two panels.

CBC — complete blood count

This counts the cells floating in your blood.

• WBC (white blood cells) — your immune system’s responders. High can suggest infection, inflammation, or stress; low can follow certain viruses or medications.
• RBC, hemoglobin, hematocrit — how well your blood carries oxygen. Low values are the usual definition of anemia and often explain fatigue or shortness of breath.
• MCV — the average size of your red cells, which helps sort out why someone is anemic (iron deficiency versus B12, for example).
• Platelets — the cells that clot. Very low or very high values get attention.

CMP — comprehensive metabolic panel

This is the chemistry of your blood.

• Glucose — blood sugar at the moment of the draw (fasting status matters).
• Creatinine and BUN, plus eGFR — how well your kidneys are filtering. eGFR is an estimate, and mild dips are common with age and dehydration.
• Sodium, potassium, chloride, CO2 — electrolytes. Potassium in particular is watched closely because it affects the heart.
• ALT, AST, alkaline phosphatase, bilirubin, albumin — liver-related values. Mildly elevated ALT and AST are extremely common and can follow alcohol, medications, fatty liver, or even a hard workout.
• Calcium — bone and nerve function, and sometimes a clue about the parathyroid glands.

What “H” and “L” really mean

A reference range is not a definition of health. It is the range that covers roughly 95% of results from the population the lab used to build it — which mathematically means about 1 in 20 healthy people will land outside it on any given test. Run a 14-value panel and the odds that something gets flagged are high even in a perfectly healthy person.

Three habits that make results easier to understand

1. Read the range next to the number, not the number alone. Lab A’s TSH range is not Lab B’s.
2. Compare against your own history. A creatinine that has sat at 1.1 for five years is a different story than one that jumped from 0.8 to 1.1 in three months.
3. Note the conditions of the draw. Fasting or not, hydration, time of day, hard exercise the night before, and supplements like biotin can all shift results.

When to call rather than wait

Portals often release results before your doctor has reviewed them, which is how people end up frightened at 11pm. Reach out promptly rather than waiting for the next visit if you see markedly low hemoglobin, a potassium or sodium far outside range, a sharp rise in creatinine, or liver enzymes several times the upper limit — especially alongside symptoms like chest pain, severe weakness, confusion, breathlessness, or yellowing skin. Otherwise, a message through the portal asking “does this change anything in my plan?” is usually the right speed.

Questions that get you a clear answer

• Which of these flagged values do you actually care about, and which are noise?
• Is this a change from my last labs?
• Does this result change my treatment, or are we just watching it?
• When should this be repeated?

If you would rather not decode a results page alone, Summara Health can read the report and explain each value in plain language, then file it in a timeline so next year’s numbers have context. See how it works.