A chemistry screen, also known as a chemistry panel or metabolic panel, is a group of blood tests which are used to evaluate a wide spectrum of conditions. The chemistry screen provides information about organ function, metabolic function, and overall health. A physician may order this panel as part of a routine physical, to evaluate the cause of a specific symptom, or to monitor an ongoing condition. The screen can contain anywhere from 7-25 tests depending on what the physician is trying to evaluate.
A patient may be asked to fast for up to 12 hours prior to blood being taken for a chemistry screen. This is because food or beverages may alter the results of the test.
Tests in a Chemistry Screen
Here are some of the tests that may be included in a chemistry panel, along with their normal values:
Electrolytes are ions in the blood that need to stay in balanced concentrations in order to maintain the body’s homeostasis. Abnormal electrolyte values can be indicative of many things, including dehydration, organ dysfunction, respiratory problems or poor hormone regulation.
- Sodium: 135-145 mmol/L
- Potassium: 3.5-5 mmol/L
- Chloride: 95-105 mmol/L
- Calcium: 2-2.6 mmol/L
- Bicarbonate: 18-22 mmol/L
A lipid profile measures the ratio of good cholesterol (HDL) to bad cholesterol (LDL) in the blood, as well as the amount of triglycerides (fat). A doctor may use this test to assess risk for heart disease.
- Total Cholesterol: 3-5.5 mmol/L
- Low-Density Lipoprotein (LDL): 85-125 mg/dL
- High-Density Lipoprotein (HDL): 40-80 mg/dL
- Triglycerides: 50-150 mg/dL
These tests measure how well the kidneys are working. If the substances measured are building up in the blood, it means that the kidneys are not filtering effectively.
- TCreatinine: 0.8-1.3 mg/dL
- Blood Urea Nitrogen (BUN): 8-21 mg/dL
Protein levels in the blood can be used to evaluate liver and kidney function as well as nutritional status.
- Albumin: 35-50 g/L
- Total Protein: 60-80 g/L
Liver Function Tests
These tests measure various liver enzymes as well as bilirubin, a waste product of the liver. Elevated liver enzymes can mean that the liver is experiencing increased activity, which can be a factor in many disease processes.
- Alanine aminotransferase (ALT): 5-30 U/L
- Alkaline phosphatase (ALP): 50-100 U/L
- Aspartate aminotransferase (AST): 5-30 U/L
- Total bilirubin: 2-20 µmol/L
Blood Glucose: 65-110 mg/dL
This test measures amount of sugar in the blood. If blood sugar is too high or too low, it can point to a dysfunction of the pancreas as in type I diabetes, or insulin resistance as in type II diabetes.
The thyroid gland helps regulate metabolism, and abnormal values on a thyroid function test can indicate that the gland is overactive (hyperthyroidism) or underactive (hypothyroidism).
- Thyroid Stimulating Hormone (TSH): 0.5-5 mIU/L
- Total T3: 0.7-1.5 ng/dL
- Total T4: 4.9-11.7 mg/dL
Some patients may find that their results are slightly out of the normal range, or seem to fluctuate over time. Some amount of variability can be normal.