Part II: Knowing the Basics of a Blood Lab, The Complete Metabolic Panel

It is more important than ever to have a basic awareness of your own health, and to have an understanding of the lab tests your doctor performs as part of a routine physical. In the February issue of Austin Fit, we discussed the Complete Blood Count (CDC), which helps to determine the overall health and nutritional status of your blood cells. This month, we’ll learn about its general-screening cousin, the Complete Metabolic Panel.

Complete Metabolic Panel
The Complete Metabolic Panel (CMP) is a general overview of major organ and body system function. It is the big picture way to look at many of the body systems and make sure they are functioning within normal limits. 

This test is performed first thing in the morning before the patient has had anything to eat—called a “fasting” blood test. As with any other test, there are normal ranges that can be reasonably wide, and within those normal ranges are optimal levels. This is the main reason why it’s important for you to have access to your lab results—to help ensure that you are not only normal, but optimal. 

A CMP test can be broken down into four main categories: a blood sugar test, liver function test, kidney function test, and electrolyte test. 

Glucose (blood sugar) Test
Glucose is a simple sugar and the major form of energy for most of your cells, including brain and muscle cells. It is the most direct way to see carbohydrate or sugar overload in your diet. With the standard American diet tending to be sugar and carbohydrate heavy, glucose is often the first indicator that more serious problems like metabolic syndrome and diabetes are looming. 

Normal values range from 70–100 milligrams per deciliter (mg/dL). Pre-diabetes is a concern in values from 100–125 mg/dL and >126 mg/dL is considered to be overt diabetes. In a healthy 20- to 50-year-old, optimal levels are in the 75–85 mg/dL range. When values start creeping toward the upper end of normal, it’s a sign that the diet isn’t optimal for that particular person. With healthy aging, normal glucose levels do slowly rise, but even a healthy 95-year-old shouldn’t be above 100.

Liver Function Test
This group of tests indicates how well the liver is working and gives early clues to dysfunction. AST (aspartate aminotransferase) and ALT (Alanine transaminase)

are the two most direct tests, both of which are liver enzymes. These enzymes become elevated if the liver is toxic, fatty, diseased, or if there is some barrier to normal liver function such as kidney stones or gallbladder disease. Both of these enzymes will rise in the presence of liver injury. AST is also present in heart tissue, so a spike in AST can be a red flag for heart injury. 

Kidney Function Test
This group of tests assesses kidney function and any deviation from normal is extremely serious. Kidney function will remain normal until function drops to roughly 25 percent, so abnormalities generally mean kidney function is severely impaired. Blood Urea Nitrogen or BUN is a measure of protein breakdown products within the bloodstream—a basic kidney function that continually eliminates these proteins. If they aren’t being eliminated properly, it’s indicative that the kidneys are struggling. Higher than normal CMP levels may be due to diminished kidney function, excessive protein in the diet, dehydration, heart attack, shock, urinary tract obstruction, or gastrointestinal bleeding. 

Creatinine is a chemical waste product of muscle metabolism, so creatinine levels in the blood are a direct indicator of how well the kidneys are filtering waste. High levels are usually due to kidney failure, urinary tract obstruction, muscle wasting, dehydration, or problems associated with pregnancy. Low levels may indicate other types of muscular or nervous system problems.

Electrolyte Test
These tests measure the levels of different electrolytes in the blood, and can point to a wide array of issues. The human body has many systems in place to protect blood electrolyte levels, so any abnormality should be taken seriously—although trends towards high and low can also indicate your hydration status. Calcium levels can indicate an overactive thyroid or thyroid overmedication, some bone disease or cancer, chronic kidney or liver disease, and also an over-supplementation of calcium. High Potassium levels may indicate an imbalance between sodium and potassium in your diet, usually favoring overly high sodium. 

High electrolyte levels may also be seen in kidney failure, red blood cell destruction, or acidosis. Low levels may indicate chronic diarrhea, diuretic use, or vomiting. Sodium is also one of the electrolytes tested. High levels may indicate fluid loss, diabetes, or adrenal gland problems. Low levels may indicate dehydration, vomiting, diarrhea, or general water imbalance.

Each test within the CMP represents a small piece of data that, when combined with other tests, can give you a rich picture of your overall health and organ functioning. By keeping copies of your blood work and noticing trends over time, you can be proactive about your health in a way you wouldn’t be able to if you only relied on your doctor for interpretation.