The capillary nail refill test is a quick test performed on the nail beds to monitor dehydration and the amount of blood flow to tissue.

Tissues need oxygen to survive. Oxygen is carried to various parts of the body by the blood (vascular) system.

This test measures how well the vascular system works in your hands and feet -- the parts of your body that are farthest from the heart.

Pressure is applied to the nail bed until it turns white, indicating that the blood has been forced from the tissue. This is called blanching. Once the tissue has blanched, pressure is removed.

While the patient holds their hand above their heart, the health care provider measures the time it takes for blood to return to the tissue, indicated by a pink color returning to the nail.

Remove colored nail polish before this test.

There will be minor pressure to the bed of your nail, which should not cause discomfort.