Chemistry screens

A chemistry screen may be done:

• As part of a routine physical examination.
• To help you and your doctor plan changes in your meal plan or lifestyle.
• To look for problems, such as a low or high blood glucose level that may be causing a specific symptom.
• To follow a specific health condition and check how well a treatment is working.
• Before you have surgery.

A health professional uses a needle to take a blood sample, usually from the arm.

How you prepare for a chemistry screen depends on what your doctor is looking for in the test.

• You may be instructed not to eat or drink anything except water for 9 to 12 hours before having your blood drawn. This is called a "fasting blood test." Fasting isn't always needed. But it may be recommended.
• In most cases, you are allowed to take your medicines with water the morning of the test.
• Do not eat high-fat foods the night before the test.
• Do not drink alcohol before you have this test.

Results are usually available in 1 to 2 days.

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

Many conditions can change chemistry screen test levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and medical history.