Blood Work Made Simple: Understanding Common Check-Up Tests

Blood Work Made Simple: Understanding Common Check-Up Tests

How to Read General Check-Up Blood Tests

by Catherina Pascale

Introduction

Blood tests are essential tools in preventive medicine. They help assess general health, screen for diseases, and provide baseline data for future comparisons. Common panels during routine check-ups include:

• Complete Blood Count (CBC)

• Basic Metabolic Panel (BMP) or Comprehensive Metabolic Panel (CMP)

• Lipid Panel

• Occasionally, Thyroid Function Tests (TFTs)

This article will guide you through each panel, explaining what is measured, typical reference ranges, and how to interpret values that are high or low.

Understanding Reference Ranges

Each laboratory result is compared to a reference (or “normal”) range. These ranges are derived statistically from healthy populations. They can vary by age, sex, ethnicity, and by laboratory methodology (e.g., instrument calibration). It is important to:

• Use the reference ranges provided by the lab that processed your test.

• Recognize that “normal” results do not guarantee perfect health; abnormal results do not always indicate disease. It is important to observe trends over time and clinical context matter (MedlinePlus, 2024). And, of course, a better understanding of the results can help you and your health care provider make decisions as to which steps are preferable in safeguarding your health.

Complete Blood Count (CBC)

What It Measures

The CBC examines several blood cell lines, providing information about oxygen transport, immune function, and clotting ability. Components include:

• Red Blood Cell (RBC) count

• Hemoglobin (Hgb)

• Hematocrit (Hct)

• Mean Corpuscular Volume (MCV)

• Mean Corpuscular Hemoglobin (MCH)

• Mean Corpuscular Hemoglobin Concentration (MCHC)

• Red Cell Distribution Width (RDW)

• White Blood Cell (WBC) count

• Differential (neutrophils, lymphocytes, monocytes, eosinophils, basophils)

• Platelet count (CBC with differential) (MedlinePlus, 2024).

Typical Reference Ranges

Below are representative reference ranges in adults. These can vary among labs. (MedlinePlus, 2024; Abimbola, 2025).

Parameter	Males	Females
RBC count	~4.3 - 5.9 million cells/µL	~3.5-5.5 million cells/µL
Hemoglobin	13.5 - 17.5 g/dL	12.0-16.0 g/dL
Hematocrit	~41 - 53%	~36-46%
WBC count	4,500 - 11,000 cells/mm³	same
MCV	80 - 100 fL (both sexes)
MCH	~26 - 34 pg
MCHC	~32 - 36 g/dL
RDW	~11 - 15%
Platelets	~150,000 - 400,000 /µL (some labs up to 450,000)

NOTE: Bleeding risk rises when platelets <50,000/µL; discuss abnormal results with your clinician.

Interpretation Highlights

• Low hemoglobin, hematocrit, or RBC count: Consistent with anemia. Subtypes: microcytic (low MCV, low MCHC) → iron deficiency or thalassemia; macrocytic (high MCV) → B12 or folate deficiency; normocytic → chronic disease or acute blood loss.

• High RBC/hemoglobin/hematocrit: May indicate polycythemia (primary or secondary) or relative dehydration.

• Elevated RDW: Suggests heterogeneity in cell size (anisocytosis), often seen in nutritional anemias.

• Low WBC: Possible causes include bone marrow suppression, certain infections, or immunodeficiency.

• High WBC: Often reflects infection or inflammation; differential cell counts can point toward bacterial versus viral causes.

• Platelet abnormalities: Low counts (thrombocytopenia) increase bleeding risk; high counts (thrombocytosis) may be reactive (e.g., inflammation) or reflect bone marrow disorders.

Basic Metabolic Panel (BMP) / Comprehensive Metabolic Panel (CMP)

Panel Overview

• The BMP measures eight substances in the blood: glucose, calcium, blood urea nitrogen (BUN), creatinine, and the electrolytes sodium, potassium, chloride, and carbon dioxide (bicarbonate). It provides information about kidney function, electrolyte and acid-base balance, and glucose metabolism (Cleveland Clinic, n.d.; WebMD, 2024).

  
  

• The CMP includes all BMP components plus tests relating to liver function: total protein, albumin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), bilirubin. (Cleveland Clinic, n.d.; WebMD, 2024).

Reference Ranges & Interpretation (General Ranges)

Typical adult ranges (general guidance; individual labs may vary). (Cleveland Clinic, n.d.; MedlinePlus, 2024):

• Glucose: ~70 - 99 mg/dL (fasting)

• Calcium: ~8.5 - 10.2 mg/dL

• BUN: ~7 - 20 mg/dL

• Creatinine: ~0.6 - 1.3 mg/dL (varies with muscle mass)

• Sodium: ~135 - 145 mEq/L

• Potassium: ~3.5 - 5.0 mEq/L

• Chloride: ~96 - 106 mEq/L

• Bicarbonate (CO₂): ~22 - 28 mEq/L

Liver function components:

• Albumin: ~3.4 - 5.4 g/dL

• Total protein: ~6.0 - 8.5 g/dL

• ALT: ~7 - 56 U/L

• AST: ~8 - 48 U/L

• ALP: ~44 - 147 U/L

• Bilirubin: ~0.1 - 1.2 mg/dL

Interpreting Values

• Elevated glucose may suggest prediabetes or diabetes.

• High BUN and creatinine often indicate impaired kidney function or possibly dehydration.

• Electrolyte abnormalities (e.g., low sodium, high potassium) can suggest issues with hydration, kidney dysfunction, or side effects of certain medications.

• Elevated liver enzymes (ALT, AST, ALP) or bilirubin may indicate liver injury, bile duct obstruction, or other hepatic pathology.

Lipid Panel

This panel evaluates cardiovascular risk by measuring:

• Total cholesterol

• High-density lipoprotein (HDL) (“good” cholesterol)

• Low-density lipoprotein (LDL) (“bad” cholesterol)

• Triglycerides

Typical desirable levels: total cholesterol under ~200 mg/dL; higher HDL; lower LDL and triglycerides are preferred (Cleveland Clinic, n.d.; MedlinePlus, 2024). Elevations in LDL or triglycerides or low HDL are associated with increased risk of heart disease and stroke.

Thyroid Function Tests (TFTs) (Optional in Routine Panel)

Often ordered if symptoms suggest a thyroid disorder. Usual components:

• Thyroid-stimulating hormone (TSH)

• Free T4; sometimes Free T3

Interpretation:

• High TSH with low T4 → hypothyroidism

• Low TSH with high T4/T3 → hyperthyroidism

Reference ranges depend heavily on assay and lab.

Interpreting Results in Context

Trends Over Time

A single test is a snapshot. Tracking values over time, ideally using the same lab methods, helps identify meaningful changes and account for normal variability. (MedlinePlus, 2024).

Clinical Correlation

Lab results must be interpreted taking into account symptoms, medical history, medications, and lifestyle. Lab values alone do not establish a diagnosis. (Cleveland Clinic, n.d.).

Asking Questions

Some useful questions to discuss with your health provider:

• What does each test measure?

• Are any values outside the reference range? If so, what might explain that (e.g., diet, hydration, medication)?

• Do I need further tests or lifestyle changes?

How This Informs General Check-Up Health

Routine blood tests provide a broad snapshot:

• Detects anemia or infection (via CBC)

• Assesses kidney or liver dysfunction, electrolyte imbalances, glucose issues (via BMP/CMP)

• Evaluates cardiovascular risk (via lipid panel)

• Screens for thyroid disorders if clinically indicated (via TFTs)

With accurate interpretation and context, patients and healthcare providers can work together to maintain or improve health.

Summary Table: Tests and Key Insights

Test Panel	Components	What Low / High Might Mean
CBC	RBC, Hgb, Hct, MCV, MCH, MCHC, RDW, WBC (with differential), platelets	Anemia, dehydration, infection, immune disorders, clotting issues
BMP/CMP	Glucose, BUN, creatinine, electrolytes; plus liver enzymes & proteins in CMP	Diabetes risk, kidney/liver dysfunction, hydration or acid-base imbalance
Lipid Panel	Total cholesterol, HDL, LDL, triglycerides	Heart disease / stroke risk
TFTs (if added)	TSH, Free T4 (± Free T3)	Hypothyroidism or hyperthyroidism depending on direction of abnormality

Please note:

The aim of this article is to help understand the values and purpose of blood tests. Always consult a health care professional for medical assistance and advice. (Reference intervals vary by laboratory, method, and patient factors like age, sex, pregnancy, altitude, medications. The ranges below are examples; always interpret results using the lab’s own reference range and with your clinician.)

References

1. Abimbola Farinde, P. (2025, July 28). Lab values, normal adult. Laboratory Reference Ranges in Healthy Adults. https://emedicine.medscape.com/article/2172316-overview?form=fpf

2. Cleveland Clinic. (n.d.). Basic metabolic panel (BMP): What it is, procedure & results. Retrieved from https://my.clevelandclinic.org/health/diagnostics/22020-basic-metabolic-panel‐bmp (Cleveland Clinic)

3. Cleveland Clinic. (n.d.). Comprehensive metabolic panel (CMP): What it is & results. Retrieved from https://my.clevelandclinic.org/health/diagnostics/22058-comprehensive-metabolic-panel‐cmp (Cleveland Clinic)

4. MedlinePlus. (2024). Complete blood count (CBC): What it is, normal results. Retrieved from https://medlineplus.gov/lab-tests/complete-blood-count-cbc/ (MedlinePlus)

5. MedlinePlus. (2024). Comprehensive metabolic panel (CMP): Lab tests. Retrieved from https://medlineplus.gov/lab-tests/comprehensive-metabolic-panel-cmp/ (MedlinePlus)

6. MedlinePlus. (2024). Basic metabolic panel (BMP): Lab tests. Retrieved from https://medlineplus.gov/lab-tests/basic-metabolic-panel-bmp/ (MedlinePlus)

7. WebMD. (2024, January 11). Comprehensive metabolic panel: Purpose, procedure, results. WebMD. https://www.webmd.com/a-to-z-guides/comprehensive-metabolic-panel