How to Do a Capillary Refill Test on Your Horse

horse showing teeth

There are many ways to check your horse for good health. A CRT is just one of the tools you can use and takes no special equipment. A capillary refill test also called a CRT or cap refill, indicates how quickly the capillaries refill at the surface of the horse's body.

Why Capillary Refills Are Important

The capillary refill test indicates how efficiently your horse's circulation system is functioning. Reduced blood circulation can be an indication of a serious health problem. These include dehydration, poor circulation due to heart problems or other conditions or illnesses.

You'll need to tie your horse safely. It may be useful to have a helper at first. Your horse should be standing quietly with its head in a normal position. If your horse is standing with its head high, it could affect the test.

To begin the capillary refill test, lift your horse's upper lip. You don't have to peel it back far, just far enough to get your fingers against its gum and see what you are doing.

Take note of the condition and color of the gums above its teeth. They should appear healthy, pink and slippery moist. Paleness, dryness or any other color than pink can be an indication of a serious problem. If there is something awry, you might want to jot down what you see, and the time you did the CRT. This may be useful to your veterinarian.

capillary refill test
If your horse doesn't like its mouth touched and handled, you'll have to teach it to stand quietly. This will make the CRT easier as well as dental work, bridling and tube deworming. Photo: 2010 K. Blocksdorf

Capillary Refill Test: Apply Pressure With a Thumb or Finger Tip

Press your thumb tip flat onto the gum just above the upper front teeth and apply pressure for a few seconds. You don't have to press really hard. Test your pressure on your own hand. If it's comfortable for you, it won't be too much pressure on your horse's gums. Hold your thumb tip down for a few seconds. You just want to hold it long enough to press the blood away from the gum surface and make it turn white. Be careful not to dig your thumbnail in. The horse should experience no discomfort from this. 

Press with your thumb on the horse's gums
K. Blocksdorf

Count to Two

Release the pressure and you will see a white 'thumbprint' where you pressed. As soon as you release, count the number of seconds it takes for the whiteness to disappear. Count: one second, two seconds. You could also use a stopwatch

The white pressure spot should disappear and the area returns to its normal healthy pink in less than two seconds. If the white spot takes longer to disappear than two seconds this can be an indication of blood loss, dehydration or shock. If it's very slow to return to normal, your horse could be in distress. Call your vet. 

If your veterinarian is examining your horse because of injury or illness (such as colic) they will do a CRT. Because you will likely be with your horse before the veterinarian arrives, being able to do a CRT yourself helps the veterinarian establish how long your horse may have been in distress. This is why it is a good idea to write down the times you found your horse to be ill, and what time you did various tests yourself like take your horse’s TPRs and the cap refill. When treating things like certain types of colic, quick treatment can result in better outcomes.

The white spot left by your thumb should disappear almost instantly on a healthy horse
K. Blocksdorf

Try a CRT a few times so that you will learn to recognize what is normal and what is not. Check the normal color and moistness of your horse's gums so you will recognize when they are not normal.

Some horses are fussy about having their mouths handled. Accustom your horse to having its lips and gums touched so you won’t have a struggle when it needs to be done.