What Can Blood Tests Find and How to Understand Results
Between CBCs, CMPs and A1Cs, a lab results page can look like alphabet soup. Brinley Beck, PA-C, UnityPoint Health, explains the most common blood tests, what they can (and can't) tell you and which require a little prep work.
What Can Blood Tests Find?
A blood test shows how different parts of your body are functioning at a specific moment in time. There's no single test that reveals everything about your health. Your provider orders specific panels based on what they're checking, whether that's organ function, hormones or blood cell counts.
- What blood test shows kidney function? A basic metabolic panel (BMP) or comprehensive metabolic panel (CMP) checks electrolytes and kidney markers to see how well your kidneys are filtering waste.
- What blood test shows liver function? A CMP includes liver enzymes and proteins that assess how well your liver is working.
- How to test blood sugar: Either a fasting glucose test (part of a BMP/CMP) or an A1C, which reflects your average blood sugar over about three months. Beck prefers A1C for screening because patients don't have to fast for it.
Which Blood Test is Best for a Full Body Checkup?
For an annual physical, Beck typically orders a CBC, CMP, lipid panel and A1C, plus a TSH for thyroid function — adding more based on symptoms or risk factors.
Complete Blood Count (CBC) Panel
A CBC gives a snapshot of your overall blood health and is commonly used to check for infection, inflammation, anemia and blood disorders.
What's included in a CBC:
- Hematocrit: Percentage of blood made up of red blood cells
- Hemoglobin: Oxygen-carrying protein in red blood cells
- Mean Corpuscular Volume (MCV): Average size of red blood cells
- Platelets: Necessary for blood clotting
- Red blood cells: Carry oxygen throughout the body
- White blood cells: Counts can signal infection, inflammation or blood disorders
What Does "CBC with Differential Abnormal" Mean?
The differential breaks white blood cells into specific types: neutrophils, lymphocytes, monocytes, eosinophils and basophils. An "abnormal" flag means one of these is outside the typical range.
"Depending on which is raised, it can clue into what type of inflammation or infection you're dealing with," Beck says. “Elevated eosinophils, for example, often point to an allergic reaction rather than infection.”
Can CBC Show Cancer?
No, it can't diagnose cancer, but an unusual white blood cell count may prompt further testing.
Basic Metabolic Panel (BMP)
A BMP evaluates electrolytes, kidney function and glucose — a quick check on how your body is managing hydration and waste.
- Electrolytes: Minerals like sodium, potassium and chloride that help regulate fluid balance, nerve signals and muscle function
- Glucose: Blood sugar level at the time of the draw
- Kidney function markers: How well your kidneys are filtering waste from the blood
Comprehensive Metabolic Panel (CMP)
A CMP includes everything in a BMP plus liver function.
Lipid Panel
A lipid panel measures cholesterol to assess stroke and heart attack risk.
What's included in a Lipid Panel:
- HDL: Good cholesterol; higher levels are protective
- LDL: Bad cholesterol; Beck says less than 100 is considered optimal
- Triglycerides: Factored into overall cardiovascular risk
Can a Blood Test Detect Cancer?
Not on its own. "No specific blood tests can really show those scary things like cancer," Beck says. "You have to look at the patient clinically."
An abnormal result, like an elevated white blood cell count, can raise a flag — but confirming cancer takes imaging or a biopsy.
Can Tumors be Detected by a Blood Test?
Some cancers release proteins called tumor markers that show up in bloodwork.
- CA 125: Monitors ovarian cancer
- CA 19-9: Monitors pancreatic cancer
- CEA (carcinoembryonic antigen): Monitors gastric and colorectal cancers
- PSA (prostate-specific antigen): Used to screen for and monitor prostate cancer
These are used mainly to track cancer treatment progress or watch for recurrence, not to diagnose. "We’re looking for a significant jump, because that’s a red flag," Beck says. A mild rise can also come from a benign condition like benign prostatic hyperplasia (BPH), a non-cancerous enlargement of the prostate that's common as men age. PSA is the exception, commonly used as a routine annual screening for men.
How to Prepare for a Fasting Blood Test
How to View Blood Test Results
Most routine blood test results take a few hours to get results.
“Some, like hemoglobin-related tests, take until the next day. Expect to see results the same day or the day after through your patient portal,” Beck says.
How to Read Blood Test Results
An out-of-range value isn't automatically a cause for alarm.
"Reference ranges change depending on the lab," Beck says. "What's a little outside the range at one facility could be within range at another."
Your provider looks at the full clinical picture, not just the number. If something's flagged, wait to hear from them before assuming the worst.
How to Get a Blood Test Near You
Blood draws can be done in several convenient locations:
- Provider’s office: Many clinics have a phlebotomist on-site
- Hospital lab: Open during regular lab hours
- Independent labs: Like LabCorp
- Walk-in care: Convenient for after hours or weekend draws
Wherever you go, start a conversation with your provider first. They’ll help determine exactly which tests you need to ensure your healthy or get you feeling better, faster.
