Fasting Blood Glucose Test: What It Is, How It Works, and How to Get Ready

A fasting blood glucose test measures the amount of sugar in your blood after you have not eaten for at least eight hours. It is one of the most common screening tests used to check for diabetes and prediabetes, and it is also used to monitor how well blood sugar is being controlled in people who already have diabetes.

A urine calcium test measures how much calcium is being excreted in your urine. Calcium is an important mineral that helps with bone health, muscle function, and nerve signaling. Normally, your kidneys filter calcium from your blood, and some of it passes into urine while the rest is reabsorbed back into the bloodstream. This test helps doctors understand if this process is working properly.

A healthcare professional will take a small sample of blood, usually from a vein in your arm, using a thin needle. The procedure typically takes only a few minutes. You may feel a quick pinch or slight sting when the needle is inserted, and a small bandage will be placed over the puncture site afterward to stop any minor bleeding.

The most common method is a 24-hour urine collection. You will receive a special container to collect all urine produced over 24 hours. During this period, it's important to follow your normal diet and activities. Keep the container refrigerated or in a cool place. After the collection period, return the container to your lab as instructed. Some labs may also use a single urine sample collected at your healthcare provider's office.

You will need to avoid eating or drinking anything except plain water for at least eight hours before the test, so most people schedule it early in the morning. Keep drinking water, since staying hydrated makes the blood draw easier. Tell your doctor about all medicines and supplements you take, because some may need to be paused or adjusted first.

Your doctor may ask you to temporarily stop certain medications before the test, such as calcium supplements, vitamin D supplements, antacids, or diuretics. Inform your doctor about all medications and supplements you take. Continue to eat and drink normally unless otherwise instructed. For a 24-hour collection, avoid swimming or activities that might contaminate the sample. Follow any specific instructions provided by your healthcare team.

Normal fasting glucose is generally between 70 and 99 mg/dL. A result of 100 to 125 mg/dL suggests prediabetes, while a reading of 126 mg/dL or higher on two separate tests usually points to diabetes. Your doctor will review your values with you, explain what they mean in your situation, and recommend next steps such as lifestyle changes, repeat testing, or treatment.

Results are typically reported as milligrams of calcium per 24 hours (mg/24hr). The normal range varies by laboratory but is generally about 100 to 300 mg per 24 hours. Your doctor will interpret your results based on your specific situation, including your diet, medications, and other test results.