D-xylose absorption test (plasma mass concentration)

This test helps your healthcare provider gather important information about your health. By measuring specific markers in your blood, it can help detect certain conditions, guide treatment decisions, and show how well your body is responding to care over time.

Your doctor may recommend this test if you have symptoms like chronic diarrhea, weight loss, or unexplained nutrient deficiencies. It can also help diagnose conditions like celiac disease, short bowel syndrome, or other intestinal malabsorption issues.

The test works by analyzing a small sample of your blood in a laboratory. Trained specialists measure the levels of specific substances in your sample, and your provider uses these results to better understand your health and determine the best next steps.

D-xylose is absorbed directly in the small intestine, so a low absorption rate suggests problems with nutrient uptake.

Before the test, your healthcare provider will explain the procedure and answer any questions you may have. You may receive specific instructions, such as whether to fast or avoid certain medications. Be sure to follow these directions closely and mention any medications, supplements, or allergies you have.

No special preparation is needed, but avoid taking medications that may affect digestion (like antibiotics or proton pump inhibitors) unless cleared by your doctor. Follow your doctor’s instructions for fasting if required.

During the test, a trained technician will clean the skin on your arm and use a small needle to draw one or more blood samples. You may feel a quick pinch or slight sting when the needle goes in, but the process is brief, and a bandage will be placed on the site afterward.

The test involves very little discomfort—only routine blood draws—and usually takes about 1–2 hours from start to finish.