Vasoactive intestinal polypeptide (VIP) is a substance found throughout the body, but the highest levels normally occur in the nervous system and gut. VIP has many functions:

• It helps control or send nerve signals
• It helps relax certain muscles along the gastrointestinal tract
• It increases the amount of water and electrolytes released from the pancreas and gut
• It triggers the release of hormones from the pancreas, gut, and hypothalamus
• It helps breakdown fat and glycogen
• It stimulates bile flow
• It blocks gastrin and gastric acid secretion

A blood test can be done to find out how much VIP you have in your blood.

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

You should not eat or drink anything for 4 hours before the test.

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

This test is used to confirm the presence of a VIPoma, a tumor that releases VIP.

Normal values range from less than 75 - 190 pg/mL (picograms per milliliter).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

A higher-than-normal level along with symptoms of watery diarrhea and flushing may be a sign of a VIPoma.

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

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

Jensen RT. Pancreatic endocrine tumors. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 205.