Your Blood Test Results Explained — A Complete Guide

Blood tests are one of the most common tools used to assess health, monitor ongoing conditions, and detect early signs of disease.
Understanding your lab results can help you have more productive conversations with your healthcare provider and make informed decisions about your health.

It’s important to remember:

• A result outside the “normal range” does not always mean something is wrong.

• Age, sex, diet, race, activity level, medications, hydration status, and even time of day can affect results.

• If you have 20–30 tests in a panel, it’s common for one or two to fall outside the reference range without indicating illness.

Lab tests should always be interpreted in the context of your medical history, symptoms, and other findings. A blood test alone can’t confirm a diagnosis — but it can provide vital clues, help monitor changes, and guide treatment or lifestyle adjustments.

Glucose & Blood Sugar Tests

• What it measures: Blood sugar (glucose) levels.

• Normal fasting range: 60–99 mg/dL.

• Diabetes diagnosis (ADA 2003): Fasting glucose ≥126 mg/dL.

• Prediabetes / impaired fasting glucose: 100–125 mg/dL.

• May also be assessed with a glucose tolerance test or hemoglobin A1c (HbA1c).

• High glucose can result from eating before the test, diabetes, certain medications, or stress.

Electrolytes

• Key electrolytes: Sodium, potassium, chloride, CO2.

• Potassium: Critical for muscle and nerve function, especially the heart. Abnormal values require medical evaluation.

• Sodium: Regulated by kidneys/adrenal glands; affected by diuretics, medications, and hydration.

• CO2 (bicarbonate): Reflects blood acidity; low levels may indicate metabolic or respiratory conditions.

Kidney Function & Waste Products

• BUN (Blood Urea Nitrogen): Waste product from protein metabolism; high values may suggest kidney problems, dehydration, or high-protein diets.

• Creatinine: Waste product from muscle metabolism; high levels may indicate impaired kidney function.

• BUN/Creatinine Ratio: Helps distinguish between different types of kidney problems. Normal adult range: 10:1 to 20:1.

• Uric Acid: Elevated levels may be linked to gout, kidney disease, or certain medications.

Liver Enzymes & Liver Function

• ALT & AST: Elevated in liver damage, hepatitis, muscle injury.

• Alkaline Phosphatase (ALP): High in bone growth, liver disease, or gallstones.

• GGT: Elevated in liver disease, especially bile duct obstruction.

• LDH: Released from damaged cells; may rise due to tissue injury or improper sample handling.

• Bilirubin: High levels may indicate liver or gallbladder issues; mild elevations can be benign (e.g., Gilbert’s syndrome).

Blood Proteins

• Albumin: Reflects nutritional status and liver/kidney function.

• Globulin: Includes antibodies important for immune defense.

• A/G Ratio: Compares albumin to globulin; imbalances may signal liver, kidney, or immune disorders.

Cholesterol & Blood Fats (Lipids)

• Total Cholesterol: <200 mg/dL is optimal.

• LDL (“bad” cholesterol): High levels increase risk of artery plaque buildup.

• HDL (“good” cholesterol): Helps remove cholesterol from arteries.

• Triglycerides: High levels linked to heart disease and pancreatitis.

• VLDL & Non-HDL Cholesterol: Additional markers for cardiovascular risk.

Cardiac Risk Markers

• C-Reactive Protein (CRP): Marker of inflammation; high-sensitivity CRP can indicate cardiovascular risk.

• Homocysteine: Elevated levels may increase risk of heart disease; often linked to vitamin B deficiencies.

• Lipoprotein(a): Genetically influenced; high levels associated with premature heart disease.

Minerals

• Calcium: Essential for bones, muscles, nerves; abnormalities may reflect parathyroid, kidney, or vitamin D issues.

• Phosphorus: Works with calcium for bone health; levels influenced by kidney function.

Thyroid Function

• TSH: Regulates thyroid activity; high = underactive, low = overactive thyroid.

• T4 & T3: Main thyroid hormones; “free” levels show active hormone available to cells.

• Thyroid Antibodies: Help detect autoimmune thyroid diseases like Hashimoto’s or Graves’.

Hormones

• Insulin & C-Peptide: Assess pancreatic function and insulin production.

• Estradiol: Main estrogen; varies with menstrual cycle, age, and hormone therapy.

• Testosterone: Important in both men and women; imbalances may indicate endocrine, reproductive, or adrenal issues.

Complete Blood Count (CBC)

• WBC (white blood cells): High in infections, low in immune suppression.

• RBC, Hemoglobin, Hematocrit: Low values indicate anemia; high values can be from dehydration or high altitude.

• MCV: Helps determine cause of anemia (iron deficiency vs. B12/folate deficiency).

• Platelets: Help with clotting; abnormal levels may be linked to bleeding/clotting disorders.

Urinalysis

• pH & Specific Gravity: Reflect acidity and concentration of urine.

• Glucose: May indicate diabetes.

• Protein: May signal kidney damage.

• Blood: May indicate infection, kidney stones, or injury.

• Nitrite & Leukocyte Esterase: Indicators of urinary tract infection.

• Microscopic Sediment: Checks for crystals, cells, bacteria.

References

1. National Kidney Foundation. Acute Kidney Injury. https://www.kidney.org/atoz/content/AcuteKidneyInjury

2. WebMD. Blood Urea Nitrogen Test. https://www.webmd.com/a-to-z-guides/blood-urea-nitrogen-test

3. Uchino S, Bellomo R, Goldsmith D. The meaning of the blood urea nitrogen/creatinine ratio in acute kidney injury. Clin Kidney J. 2012;5(2):187–191. doi:10.1093/ckj/sfs013

4. Salvador LG et al. A low BUN/creatinine ratio predicts histologically confirmed acute interstitial nephritis. BMC Nephrol. 2023;24(1):75. doi:10.1186/s12882-023-03118-0

5. Sujino Y et al. Clinical implications of the blood urea nitrogen/creatinine ratio in heart failure. ESC Heart Fail. 2019;6(6):1274–1282.

6. Shen S, Yan X, Xu B. The BUN/creatinine ratio and all-cause mortality. Ren Fail. 2022;44(1):184–190.

7. Ok F et al. Predictive values of BUN/creatinine ratio in COVID-19 severity. J Med Virol. 2021;93(2):786–793.

8. Hosten AO. BUN and Creatinine. In: Walker HK et al., eds. Clinical Methods. 3rd ed. Boston: Butterworths; 1990.

9. Matsue Y et al. BUN/creatinine ratio in general population and acute heart failure. Heart. 2017;103(6):407–413.