Blood Chemistry: What You Need to Know

Patients now have direct access to web based portals containing information from their doctor’s offices. Do you ever wonder what those blood chemical tests mean? One of the most basic laboratory tests done in a physician’s office is the Basic Metabolic Profile (BMP). This test measures the sodium, potassium, chloride, carbon dioxide content, glucose (sugar), creatinine and blood urea nitrogen (BUN) found in blood.

Creatinine & BUN. These two chemicals reflect your kidney function. By using these two chemicals, you can calculate your estimated glomerular filtration rate (eGFR), which is roughly a percentage of normal kidney function. The eGFR does decline with aging, so we rarely have 100% normal kidney function.

Glucose. This is the level of sugar in blood. This test is used to screen for diabetes and low blood sugar. The 8-hour fasting blood sugar should be less than 100 milligrams per deciliter (mg/dl). If the blood sugar is elevated, this could be concerning for diabetes or pre-diabetes. If the blood sugar is more than 200 two hours after eating, this could also be concerning for diabetes.

Sodium. The sodium concentration in blood should be between 135 and 145 milliequivalents per liter (mEq/L). The sodium concentration is determined by the kidneys and commonly reflects the amount of water in blood. If there is an excess of water in the blood, then the sodium concentration will be lower. If there is a deficit of water in the blood, then the sodium concentration will be high. Your physician must then determine why you have a water problem and this requires further testing.

Potassium. The potassium concentration in blood is regulated by many processes including kidney function, acid in blood, glucose, insulin, and adrenalin in blood. The normal concentration of potassium in the blood is 3.5 to 5.5 milliequivalents per liter (mEq/L). Potassium in blood is very important for muscle and heart function. If there is an abnormal level of potassium in blood, this should be evaluated and treated promptly by your physician. A low potassium can often be treated with supplementation. If the potassium is high, this suggests significant problems for your muscles and heart and must be evaluated and treated promptly. Learn about your risks for high blood potassium levels. You can also see my prior post.

Chloride & Carbon Dioxide Content. These two chemicals reflect acid and alkali that are dissolved in blood. The lungs and kidneys regulate these levels in blood. The normal chloride concentration is between 96 and 106 mEq/L. The normal carbon dioxide content in blood is between 22 and 29 mEq/L. Changes in the carbon dioxide content in blood often reflect the change in bicarbonate levels in the blood. As bicarbonate levels vary, this will cause a change in chloride levels as well. Acids can build up because of diabetes, lung disease, kidney disease, poisoning and shock. It is possible to get clues about what is causing an acid or alkali build up in the blood by examining the relationship between the chloride and carbon dioxide levels. Your physician must make this analysis.

These blood tests are very important in monitoring the health of several organ systems in the body, but most specifically, how well your kidneys are functioning to control the metabolic environment of your body. Learn more about kidney disease.

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