A mononucleosis spot (or Monospot) test is a blood test used to determine whether you have contracted the Epstein-Barr virus, the virus that causes infectious mononucleosis. Your doctor may order this test if you have symptoms of mononucleosis.

Mononucleosis is a viral disease that affects certain blood cells and creates flu-like symptoms.

Mononucleosis is a viral infection caused by the Epstein-Barr virus (EBV), which is a type of herpes virus and one of the most common human viruses. Also called “mono” and “the kissing disease,” the illness isn’t considered serious or life threatening.

This disease typically affects teenagers and young adults in their 20s. The symptoms of infectious mononucleosis can make it difficult to continue with normal daily activities. Symptoms may last from several weeks to a couple of months. In rare cases, it can last several months.

Symptoms of mononucleosis include:

  • fever
  • sore throat
  • swollen glands in neck and armpits
  • severe fatigue
  • body aches
  • headaches
  • loss of appetite
  • rash
  • swollen spleen, liver, or both (uncommon)

If you have these symptoms for a week or longer, you may have mono. Your doctor may perform the mononucleosis spot test to confirm (or rule out) the diagnosis.

When a virus infects the body, the immune system goes to work to fight it off. This is your body’s protective reaction. It includes the release of certain antibodies, or “fighter cells,” charged with going after the viral cells.

The mononucleosis test looks for the presence of two antibodies that typically form when certain infections — like those caused by the Epstein-Barr virus — are present in the body.

On rare occasions, the test may show antibodies even though you don’t have the infection. This may occur especially if you have:

If the test comes back negative, it may mean you don’t have the infection or that the test was performed too early or too late to detect the antibodies. Your doctor might recommend a second test in a couple weeks or may try other tests to confirm the diagnosis.

Note: The Centers for Disease Control and Prevention (CDC) doesn’t recommend the Monospot test for general use because, while it may indicate whether you have infectious mononucleosis, it doesn’t confirm the presence of the Epstein-Barr virus.

This blood test is most often done once symptoms have developed, which is typically 4 to 6 weeks after exposure (this delay is referred to as the incubation period). The test helps to confirm a diagnosis of the illness.

Like most blood tests, it’s performed by a healthcare provider who draws a blood sample from a vein, usually on the inside of the elbow or the back of the hand. Sometimes a simple finger-prick test may be used instead.

Your healthcare provider will wrap an elastic band around your upper arm to make the vein fill with blood. They’ll then gently insert a small needle into the vein, allowing the blood to flow into an attached tube.

When the tube contains enough blood, your doctor will withdraw the needle and cover the small puncture wound with a bandage.

For a finger-prick test, your healthcare provider will make a small prick in the tip of your ring finger, then squeeze to collect enough blood in a small tube to perform the test. A bandage is placed over the small wound afterward.

Lab technicians place the blood sample on a microscope slide, mix it with other substances, and then watch to see if the blood begins to clump. If it does, the test is considered a positive confirmation of mononucleosis.

Though blood tests are extremely safe, some people may feel lightheaded after it’s over. If you experience lightheadedness, tell your healthcare provider, and sit down in the office until it passes. They may also get you a snack and a beverage to help you recover.

Other complications may include soreness at the injection site, particularly if your healthcare provider had a hard time reaching your veins. Obtaining a blood sample can sometimes be difficult if the vein is particularly small or difficult to see.

You may also have a slight risk of hematoma, which is basically a bruise. This will typically heal on its own after a few days. A warm compress may help if you notice any swelling.

As with all procedures that create an opening in the skin, there’s a rare chance of infection.

Your healthcare provider will use an alcohol swab to wipe the place of insertion beforehand, which almost always prevents infections. However, you should watch for any swelling or pus, and be sure to keep the needle entry site clean after you go home.

Finally, if you have any bleeding disorders or if you are taking blood-thinning medications like warfarin or aspirin, be sure to tell your doctor before the test.

A positive test result means that the antibodies charged with attacking the Epstein-Barr virus were detected in your blood and that you most likely carry the virus.

If your doctor determines you that have mononucleosis, they’ll likely tell you to rest, drink plenty of fluids, and take a pain reliever to lower a fever.

While there’s no specific vaccine or treatment for mono, your doctor may treat you for complications that might result from the infection. If your spleen is enlarged, you should avoid contact sports and strenuous activities.