Your Lab Results Decoded
Wonder what all those numbers mean? So did we
En español l How’s your bilirubin level? And your BUN/creatinine ratio? Unless you enjoy reading Dictionary of Medical Terms, your routine lab results can seem downright cryptic. To help you decipher them, we asked Mark S. Lachs, M.D., author of Treat Me, Not My Age, and Marie A. Bernard, M.D., deputy director of the National Institute on Aging, to explain what all those numbers really mean.
Just be aware: Abnormal test results are fairly common, especially among older adults. “Fifty-plus folks tend to take more medications,” says Lachs, “and that can throw off test results. For example, diuretics can alter sodium and potassium levels; heparin can decrease your platelet count.” (These are real abnormalities that may need further treatment.) Plus, many older adults have chronic conditions that require more frequent testing — and the more you’re tested, the greater the likelihood of error. Finally, normal ranges are based on population averages, so normal for you might be slightly out of that range and of no significance. For instance, if you have Gilbert’s syndrome, a common, mild liver condition, you’d show elevated bilirubin, which could otherwise signal a serious liver dysfunction. “If you have known abnormalities, be sure to remind your doctor each time you get tested,” says Lachs.
It’s a good idea to schedule a doctor’s appointment after undergoing lab work. That way, you can discuss any unusual results face-to-face.
What it is
Sugar in the blood
Normal Results
70 - 99 mg/dl
What a low number may mean
Hypoglycemia, liver disease, adrenal insufficiency, excess insulin
What a high number may mean
Hyperglycemia, certain types of diabetes, prediabetes, pancreatitis, hyperthyroidism
What it is
An electrolyte, which keeps your body in balance
Normal results
136 - 144 mEq/L
What a low number may mean
Use of diuretics, diarrhea, adrenal insufficiency
What a high number may mean
Kidney dysfunction, dehydration, Cushing's syndrome
What it is
An electrolyte and mineral
Normal results
3.7 - 5.2 mEq/L
What a low number may mean
Use of diuretics or corticosteroids (such as prednisone or cortisone)
What a high number may mean
Acute or chronic kidney failure, Addison's disease, diabetes, dehydration
What it is
An electrolyte
Normal results
96 - 106 mmol/L
What a low number may mean
Emphysema, chronic lung diseases
What a high number may mean
Dehydration, Cushing's syndrome, kidney disease
What it is
Gaseous waste product from metabolism
Normal results
20 - 29 mmol/L
What a low number may mean
Kidney disease, certain toxic exposures, severe infection
What a high number may mean
Lung diseases, including COPD
What it is
A waste product formed in liver and carried to kidneys, filtered out of blood, excreted through urine.
Normal results
7 - 29 mg/dL
What a low number may mean
Malnutrition
What a high number may mean
Liver or kidney disease, heart failure
What it is
A chemical waste produced by muscle metabolism
Normal results
0.8 - 1.4 mg/dL
What a low number may mean
Low muscle mass, malnutrition
What a high number may mean
Chronic or temporary decrease in kidney function
Normal results
10:1 to 20:1
What a low number may mean
Malnutrition
What a high number may mean
Blood in bowels, kidney obstruction, dehydration
What it is
A mineral stored in the hard part of bones
Normal results
8.5 - 10.9 mg/dL
What a low number may mean
Calcium, magnesium, or Vitamin D deficiency; malnutrition;pancreatitis; neurological disorders
What a high number may mean
Kidney disease, hyperparathyroidism, cancer, excess vitamin D intake
What it is
Chains of amino acids essential for the growth and repair of cells
Normal results
6.3 - 7.9 g/dL
What a low number may mean
Malnutrition, liver or kidney disease
What a high number may mean
Liver or kidney disease, dehydration, multiple myeloma
What it is
Protein that keeps fluid from leaking out of blood vessels and that nourishestissues and transports nutrients through the body
Normal results
3.9 - 5.0 g/dL
What a low number may mean
Liver or kidney disease, malnutrition
What a high number may mean
Dehydration
What it is
A pigment in the bile, a digestive fluid produced by the liver
Normal results
0.2 - 1.9 mg/dL
What a low number may mean
Generally not a concern
What a high number may mean
Liver disease, bile duct disorder or red cell destruction
What it is
Enzyme found in the liver and bones
Normal Results
44 - 147 IU/L
What a low number may mean
Malnutrition
What a high number may mean
Paget's disease or certain cancers that spread to bone, bile duct obstruction, liver cancer
What it is
Enzyme found mostly in the liver
Normal Results
8 - 37 IU/L
What a low number may mean
Generally not a concern
What a high number may mean
Certain toxins such as excess acetaminophen or alcohol, hepatitis
What it is
Enzyme found in liver, muscle, and other tissues
Normal results
10 - 34 IU/L
What a low number may mean
Generally not a concern
What a high number may mean
Excess acetaminophen, hepatitis, muscle injury
What it is
White blood cells defend the body against infection
Normal results
4,500 - 10,000 cells/mcL
What a low number may mean
Autoimmune illness, bone marrow failure, chemotherapy, viral
infections
What a high number may mean
Infection, inflammation, cancer, leukemia, intense exercise, stress,
corticosteroids
What it is
Red blood cells pick up oxygen from the blood and deliver it to tissues
throughout the body
Normal results
Male: 4.7 - 6.1 Mill/mcL
Female: 4.2 - 5.4 Mill/mcL
What a low number may mean
Iron, vitamin B12, or folate deficiency; bone marrow
damage
What a high number may mean
Dehydration, renal problems, pulmonary or congenital heart disease
What it is
Oxyrgen-carrying pigment in red blood cells
Normal results
Male: 13.8 - 17.2 g/dL
Female: 12.1 - 15.1 g/dL
What a low number may mean
Iron, vitamin B12, or folate deficiency; bone marrow damage
What a high number may mean
Dehydration, renal problems, pulmonary or congenital heart disease
What it is
The percentage of red blood cells in the blood
Normal Results
Male: 40.7% - 50.3%
Female: 36.1% - 44.3%
What a low number may mean
Iron, vitamin B12, or folate deficiency; bone marrow
damage
What a high number may mean
Dehydration, renal problems, pulmonary or congenital heart disease
What it is
Average size of red blood cells
Normal results
80 - 95 fL
What a low number may mean
Iron deficiency
What a high number may mean
Vitamin B12 or folate deficiency
What it is
The amount of hemoglobin in red blood cells
Normal Results
27 - 31 pg
What a low number may mean
Iron deficiency
What a high number may mean
Vitamin B12 or folate deficiency
What it is
Measures number of platelets — colorless blood cells integral to clotting
Normal Results
150 - 400 Thous/mcL
What a low number may mean
Viral infections, lupus, leukemia, chemotherapy, pernicious anemia (due to vitamin B12 deficiency)
What a high number may mean
Leukemia, myeloproliferative disorders (which cause blood cells to grow abnormally in bone marrow), inflammatory conditions
Total Cholesterol
<200 mg/dL
HDL
>40 mg/dL
LDL
<130 mg/dL
Triglycerides
<150 mg/dL
Photo by Science Photo Library/Getty Images
Frequent testing increases the likelihood of error.
These factors can throw off results:
- Running or any high-intensity exercise can cause slight dehydration and show up as kidney insufficiency.
- A sunburn can elevate white blood cell count, which typically signals inflammation.
- Got a sick spouse or child but feel fine yourself? A nonsymptomatic cold virus can raise or lower white blood cell count.
- An improper blood draw can cause a potassium spike; eating too much licorice can make it drop.
- A specimen that sits for too long before testing by the lab can skew blood sugar readings.
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Also of interest: How to get patients to ask — and doctors to listen.