D-xylose/Glucose Absorption Test – Indications, Procedures, Results

Last updated: February 8, 2026 Medically reviewed by: RxHarun Orthopedic Specialist Doctor Reading time: 3 min read

Xylose tolerance test; Diarrhea – xylose; Malnutrition – xylose; Sprue – xylose; Celiac – xylose

D-xylose absorption is a laboratory test to determine how well the intestines absorb a simple sugar (D-xylose). The test helps determine if nutrients are being properly absorbed.

How the Test is Performed

The test requires a blood and urine sample. These tests include:

Clean catch urine specimen
Venipuncture (blood draw)

There are several ways to perform this test. A typical procedure is described below, but make sure you follow the specific instructions you are given.

You will be asked to drink 8 ounces (240 ml) of water that contains 25 grams of sugar called d-xylose. The amount of d-xylose that comes out in your urine over the next 5 hours will be measured. You may have a blood sample collected at 1 and 3 hours after drinking the liquid. The amount of urine you produce over a 5-hour period is also determined. Your health care provider will tell you how to collect all of the urine during a 5-hour period.

How to Prepare for the Test

Do not eat or drink anything (even water) for 8 to 12 hours before the test. Do not exercise before the test. A failure to restrict activity may affect test results.

Your provider may tell you to stop taking certain drugs that can affect test results. Drugs that can affect test results include aspirin, atropine, indomethacin, isocarboxazid, and phenelzine. Never stop taking any medicine without first talking to your doctor.

How the Test will Feel

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

Urine is collected as part of normal urination with no discomfort.

Why the Test is Performed

Your provider may order this test if you have:

Persistent diarrhea
Signs of malnutrition
Unexplained weight loss

This test is primarily used to determine if nutrient absorption problems are due to a disease of the intestines.

Normal Results

A normal result depends on how much D-xylose is given. In most cases, the test results are either positive or negative. A positive result means that D-xylose is found in the blood or urine and is therefore being absorbed by the intestines.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Lower than normal values may be seen in:

Celiac disease (sprue)
Crohn disease
Giardia lamblia infestation
Hookworm infestation
Lymphatic obstruction
Radiation enteropathy
Small intestinal bacterial overgrowth
Viral gastroenteritis
Whipple disease

Risks

Risks associated with having blood drawn are slight, but may include:

Excessive bleeding
Fainting or feeling lightheaded
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)

Considerations

Multiple tests may be necessary to determine the reason for malabsorption .

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

Add references, clinical guidelines, textbooks, journal articles, or trusted medical sources here. You can edit this area later with a custom field named _rx_references.

Written by Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist

Dr. Md. Harun Ar Rashid, MPH, MD, PhD, is a highly respected medical specialist celebrated for his exceptional clinical expertise and unwavering commitment to patient care. With advanced qualifications including MPH, MD, and PhD, he integrates cutting-edge research with a compassionate approach to medicine, ensuring that every patient receives personalized and effective treatment. His extensive training and hands-on experience enable him to diagnose complex conditions accurately and develop innovative treatment strategies tailored to individual needs. In addition to his clinical practice, Dr. Harun Ar Rashid is dedicated to medical education and research, writing and inventory creative thinking, innovative idea, critical care managementing make in his community to outreach, often participating in initiatives that promote health awareness and advance medical knowledge. His career is a testament to the high standards represented by his credentials, and he continues to contribute significantly to his field, driving improvements in both patient outcomes and healthcare practices. Born and educated in Bangladesh, Dr. Rashid earned his BPT from the University of Dhaka before pursuing postgraduate training internationally. He completed his MD in Internal Medicine at King’s College London, where he developed a special interest in inflammatory arthritis and metabolic bone disease. He then undertook a PhD in Orthopedic Science at the University of Oxford, conducting pioneering research on cytokine signaling pathways in rheumatoid arthritis. Following his doctoral studies, Dr. Rashid returned to clinical work with a fellowship in interventional pain management at the Rx University School of Medicine, refining his skills in image-guided joint injections and minimally invasive pain-relief techniques.