--- title: "CBC vs CMP: What Each Blood Panel Measures, How They Differ, and Why Annual Blood Work Usually Includes Both" type: guide url: "https://www.test-well.com/guides/cbc-vs-cmp" date_published: 2026-09-28 reviewed_at: 2026-09-28 --- # CBC vs CMP: What Each Blood Panel Measures, How They Differ, and Why Annual Blood Work Usually Includes Both *A CBC counts the cells in your blood. A CMP measures the chemistry dissolved in the fluid around them. They overlap on nothing, which is exactly why they are ordered together — and why neither one alone is a 'full blood test.'* > A CBC (complete blood count) counts and sizes your blood cells — red cells and hemoglobin for anemia, white cells for infection and immunity, platelets for clotting. A CMP (comprehensive metabolic panel) measures 14 chemicals in the liquid part of blood — glucose, kidney function, electrolytes, liver enzymes and proteins. They share no values, so one cannot substitute for the other; together they are the standard baseline for annual blood work. Neither includes cholesterol, thyroid, vitamins or hormones — those are separate tests. ## Recommended tests | Recommended | Type | Price | Why | | --- | --- | --- | --- | | [CBC with Differential](https://www.test-well.com/tests/cbc-with-differential) | Test | $21.99 | The cell count — with the white-cell breakdown included | | [Comprehensive Metabolic Panel](https://www.test-well.com/tests/comprehensive-metabolic-panel) | Test | $22.99 | The chemistry — glucose, kidney, liver, electrolytes | | [Essential Health Panel](https://www.test-well.com/tests/essential-health-panel) | Panel (10 tests) | $189.99 | CBC and CMP with lipids, A1c, TSH and more in one draw | | [General Wellness Panel](https://www.test-well.com/tests/general-wellness-panel) | Panel (4 tests) | $49.99 | The compact annual baseline | All prices are cash-pay plus one $6 lab processing fee per order; physician authorization is included. ## The One-Paragraph Answer Blood is cells suspended in fluid. The **CBC** looks at the cells: how many red cells you have and how much hemoglobin they carry, how many white cells and (with a differential) of which types, and how many platelets. The **CMP** looks at the fluid: sugar, salts, waste products the kidneys clear, and the enzymes and proteins that reflect liver function. A CBC can tell you that you are anemic; it cannot tell you your kidney function. A CMP can tell you your liver enzymes are up; it cannot tell you your white count. Annual blood work includes both because each covers what the other cannot. ## What a CBC Measures A complete blood count reports the three cell lines and their characteristics. **Red cells:** the count, hemoglobin (the oxygen-carrying protein — the number that defines anemia), hematocrit (the fraction of blood that is red cells) and the red-cell indices — MCV (average cell size), MCH and MCHC (hemoglobin per cell), and RDW (variation in size) — which point to the cause of an anemia before any further test. **White cells:** the total count, and in a CBC with differential the breakdown into neutrophils, lymphocytes, monocytes, eosinophils and basophils, which separates bacterial from viral infection, flags allergy, and catches the rare blood cancer. **Platelets:** the count, and often the mean platelet volume. A CBC is the test for fatigue that might be anemia, for infections, for unexplained bruising or bleeding, for monitoring medications that affect the marrow, and as a general baseline. It requires no fasting. TestWell's [CBC with Differential](https://www.test-well.com/tests/cbc-with-differential) includes the white-cell breakdown; the plain [CBC](https://www.test-well.com/tests/cbc) does not — the [difference is explained here](https://www.test-well.com/guides/cbc-vs-cbc-with-differential). The [CBC explainer](https://www.test-well.com/guides/cbc-with-differential-explained) walks through every value. ## What a CMP Measures A comprehensive metabolic panel reports 14 chemistry values from the fluid part of blood, in four groups. **Blood sugar:** glucose. **Kidney:** BUN and creatinine, with eGFR calculated from creatinine. **Electrolytes and acid–base:** sodium, potassium, chloride, bicarbonate (reported as CO2) and calcium. **Liver and proteins:** ALT, AST, alkaline phosphatase, total bilirubin, albumin and total protein. Together they screen for diabetes and prediabetes, kidney disease, electrolyte problems, dehydration, and liver stress from alcohol, fat, medications or hepatitis. A CMP is the test for annual metabolic screening, for monitoring medications that affect the kidneys or liver (statins, blood pressure drugs, metformin, methotrexate, GLP-1s, isotretinoin, testosterone), and for symptoms such as excessive thirst, swelling, fatigue or abdominal discomfort. Fast for 8–12 hours so the glucose value reads against its fasting range; the other 13 values are valid either way. The [CMP](https://www.test-well.com/tests/comprehensive-metabolic-panel) page has each component; the [CMP vs BMP guide](https://www.test-well.com/guides/cmp-vs-bmp) explains the smaller 8-value version. ## CBC vs CMP: Side by Side | | CBC (complete blood count) | CMP (comprehensive metabolic panel) | | --- | --- | --- | | What it examines | The cells in blood | The chemistry of the fluid | | Values | ~10 (about 15 with differential) | 14 | | Answers | Anemia and its type; infection and immune status; platelet/clotting counts; blood cancers | Diabetes and prediabetes; kidney function; electrolytes and hydration; liver health; protein status | | Does not cover | Any chemistry — kidney, liver, glucose, electrolytes | Any cell count — anemia, white cells, platelets | | Fasting | Not required | 8–12 hours preferred (for glucose) | | Sample | Whole blood (lavender tube) | Serum (gold/red tube) | | Typical use | Fatigue, infection, bruising, medication monitoring, baseline | Annual screening, medication monitoring, thirst/swelling/fatigue work-up, baseline | Neither panel includes cholesterol (lipid panel), average blood sugar (hemoglobin A1c), thyroid (TSH), vitamins (D, B12, ferritin/iron) or hormones. Those are the usual additions to a CBC and CMP when building annual blood work. ## Which Should You Order? - **Annual baseline, feeling well:** both. They are the two least expensive, highest-yield panels in the catalog and they do not overlap. Add a lipid panel and A1c for the standard "annual physical" set — the [General Wellness Panel](https://www.test-well.com/tests/general-wellness-panel) and [Essential Health Panel](https://www.test-well.com/tests/essential-health-panel) bundle them. - **Fatigue:** both, plus ferritin, TSH and vitamin D — anemia (CBC), kidney or liver or glucose problems (CMP), iron stores and thyroid (the additions) cover the common causes in one draw. - **Fever, recurrent infections, or you want to know whether an infection is bacterial or viral:** CBC with differential; the CMP adds nothing here unless dehydration or kidney involvement is a concern. - **Monitoring a medication:** depends on the drug. Statins, metformin, blood pressure medication, GLP-1s, isotretinoin: CMP. Methotrexate, chemotherapy, clozapine, carbamazepine: both (marrow and liver). Testosterone therapy: CBC (hematocrit) and CMP together. - **Excessive thirst, urination, swelling, or a family history of diabetes or kidney disease:** CMP, fasting, with A1c. - **Easy bruising, bleeding, pale skin:** CBC first; a CMP is added if liver disease is a possibility, since the liver makes clotting factors. ## How to Read Them Together The two panels are most useful when read as a pair, because several common problems leave marks on both: - **Low hemoglobin (CBC) with high creatinine or low eGFR (CMP):** anemia of kidney disease — the kidneys make the hormone that drives red-cell production. - **Low hemoglobin with a high MCV (CBC) and raised AST/ALT or GGT (CMP):** a pattern common with heavy alcohol use or liver disease; B12 and folate are checked too. - **High white count with neutrophils up (CBC) and low bicarbonate or high BUN (CMP):** a significant infection with dehydration or early sepsis — a same-day medical evaluation, not a lab follow-up. - **Low platelets (CBC) with low albumin and raised bilirubin (CMP):** the combination that raises concern for advanced liver disease. - **High hematocrit (CBC) with high sodium and BUN (CMP):** dehydration concentrating everything — repeat after drinking normally before reading anything else into it. - **Everything normal on both:** the common result, and a genuinely useful one — it excludes anemia, infection, kidney disease, liver disease and diabetes as explanations for symptoms, and turns the search toward thyroid, iron stores, vitamins, sleep and hormones. One draw covers both panels — they come from different tubes filled at the same visit. Fast 8–12 hours if the CMP is included; water, and black coffee if you must, are fine. ## What to Do With the Result Most out-of-range values on a CBC or CMP are mild, and the first move is to look at the pattern and repeat anything unexpected. A single mildly low hemoglobin is followed by ferritin and iron studies; a mildly raised ALT by a review of alcohol, weight and medications and a repeat in a few weeks; a fasting glucose of 100–125 by an A1c; a low eGFR by a repeat in three months, since kidney disease is defined by persistence. Values far outside the range — a hemoglobin under 8, a potassium above 6 or below 3, a platelet count under 50, a creatinine that has doubled — need prompt medical attention rather than a recheck. Both panels are routine draws at Quest and Labcorp, orderable through TestWell with physician review, with results in one to three business days and the laboratory's reference ranges on the report. ## Frequently asked questions ### What is the difference between a CBC and a CMP? A CBC counts and characterizes blood cells — red cells and hemoglobin, white cells, platelets — and answers questions about anemia, infection and clotting. A CMP measures 14 chemicals in the liquid part of blood — glucose, kidney markers, electrolytes, liver enzymes and proteins — and answers questions about diabetes, kidney and liver function and hydration. They share no values. ### Do I need both a CBC and a CMP? For annual blood work or a fatigue work-up, yes — each covers what the other cannot, and together they are the standard baseline. For a specific question you may need only one: infection or bruising points to the CBC, thirst or a medication check to the CMP. ### Does a CBC or CMP check cholesterol, thyroid or vitamins? No. Cholesterol is a lipid panel, average blood sugar is hemoglobin A1c, thyroid is TSH, and vitamins and iron are separate tests. A complete annual set usually adds a lipid panel and A1c to the CBC and CMP, with ferritin, vitamin D and TSH as common additions. ### Do I have to fast for a CBC or CMP? The CBC does not require fasting. The CMP includes glucose, whose reference range is a fasting range, so fast 8–12 hours if you can; the other 13 values are valid either way. Water is fine. ### Is a CBC or CMP a 'full blood test'? Neither is. Together they are the foundation — cells and chemistry — but a full picture of routine health adds a lipid panel, A1c and usually TSH, with ferritin and vitamin D as common extras. TestWell's wellness panels bundle those combinations into one draw. ### Which is more important, CBC or CMP? It depends on the question. For infection, anemia or bleeding, the CBC. For diabetes, kidney or liver health, or medication monitoring, the CMP. For a general baseline they are equally important, and their combined cost is low enough that choosing between them rarely makes sense. ## Sources - [MedlinePlus (NIH) — Complete Blood Count (CBC)](https://medlineplus.gov/lab-tests/complete-blood-count-cbc/) - [MedlinePlus (NIH) — Comprehensive Metabolic Panel (CMP)](https://medlineplus.gov/lab-tests/comprehensive-metabolic-panel-cmp/) - [American Association for Clinical Chemistry — Lab Tests Online: CBC; CMP](https://www.testing.com/tests/complete-blood-count-cbc/) - [US Preventive Services Task Force — Recommendations relevant to routine screening (glucose, lipids, kidney)](https://www.uspreventiveservicestaskforce.org/uspstf/recommendation-topics) --- Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-28. Review policy: https://www.test-well.com/reviewers/youmna-distefano-md Canonical page: https://www.test-well.com/guides/cbc-vs-cmp Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.