How Thrush Is Diagnosed

Most of the time, your healthcare provider can diagnose thrush by examining your mouth and throat. A condition most common in babies, older adults, and people with suppressed immune systems, thrush is marked by the overgrowth of a fungus called candida in the mouth and throat.

In some cases, however, your doctor may need to take a sample from those areas then send that sample to a laboratory for testing. In more severe cases in which thrush has spread to your esophagus, you may need to undergo a medical imaging procedure called endoscopy.

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At-Home Testing

Although it’s often difficult to detect on your own, thrush usually manifests in symptoms such as a white coating on the inside of your mouth and throat, a cottony sensation in the mouth, soreness, and/or loss of taste.

Certain self-checks are said to aid in diagnosis. However, there’s no scientific support for them. They include a practice called “the candida spit test,” which involves spitting into a clear glass of water immediately after waking. Proponents suggest that saliva that sinks to the bottom of the glass—or turns the surrounding water cloudy—may signal the presence of thrush, but this may not be true.

Lab Tests

If you suspect that you might have thrush, your doctor may be able to diagnose the condition with a simple examination of your mouth and throat. However, your doctor may need to take a sample of one of your affected areas in the mouth (also known as lesions), then examine that sample under a microscope. These samples typically involve a gentle, painless scraping.

Throat Culture

In some cases, healthcare providers may use a throat culture in the diagnosis of thrush. This procedure involves using a cotton swab to collect a sample from the back of your throat. The sample is then sent to a laboratory, where it’s placed in a special environment to promote cell growth. The culture is then analyzed.

While the swabbing of your throat may be briefly uncomfortable, it’s unlikely to cause pain.

Other Tests

Because thrush can sometimes indicate an underlying health issue (such as diabetes), your doctor may perform further testing such as blood tests.

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Imaging Tests

To diagnose thrush in the esophagus, healthcare providers use an imaging test called endoscopy. This technique involves examining the esophagus, stomach, and upper part of your small intestine through the use of an endoscope: a flexible, lighted tube equipped with a camera at the end.

What to Expect

Often provided by a gastroenterologist, endoscopy is generally performed in a hospital or an outpatient center. The procedure usually takes between 15 and 30 minutes.

To help you relax during your endoscopy, you’ll most likely receive a light sedative (often given through an intravenous needle in your arm). Since the sedatives administered prior to endoscopy take up to 24 hours to wear off, you’ll need to arrange for a ride home from the hospital or outpatient center.

For your endoscopy, you’ll lie on your side on an exam table while your doctor passes the endoscope down your esophagus and into your stomach. During the procedure, the small camera at the end of the endoscope will transmit a video image to a monitor. This allows your doctor to obtain a close examination of the lining of your upper GI tract.

At this time, your doctor may also perform a biopsy (i.e., the removal of cells or tissue). Later on, a pathologist will examine your cells or tissue to check for disease.

Some people experience symptoms such as bloating or nausea for a short time after undergoing endoscopy. In addition, you may have a sore throat for one or two days.

Although some results from your endoscopy may be available right away, biopsy results will take a few days longer.

Potential Risks

While endoscopy is a safe procedure, it does carry the risk of the following complications:

  • bleeding from the site where your doctor took the tissue samples
  • perforation in the lining of your upper GI tract
  • an abnormal reaction to the sedative, including breathing or heart problems

If you experience any of the following issues after undergoing endoscopy, seek immediate medical attention:

  • chest pain
  • difficulty breathing
  • problems swallowing, or throat pain that gets worse
  • vomiting
  • pain in your abdomen that gets worse
  • bloody or black, tar-colored stool
  • fever

Differential Diagnosis

In some cases, thrush may cause symptoms similar to those associated with other illnesses. For that reason, your doctor may consider the following conditions when evaluating you or your child for a possible case of thrush:

Frequently Asked Questions

How is thrush diagnosed?

Thrush can often be diagnosed by its appearance, but it can be quickly confirmed by taking a scraping from the mouth, genitals, or skin and looking for signs of the fungus under a microscope using a 10% potassium hydroxide (KOH) solution. The KOH solution dissolves skin cells while leaving Candida fungus cells intact.

What does thrush look like?

Oral candidiasis causes whitish patches around the mouth, throat, and/or tongue, often with redness and irritation. Vaginal candidiasis causes burning, itching, redness, soreness, and a cottage cheese-like discharge with a yeasty smell. Penile candidiasis causes redness, itching, soreness, and swelling of the penis head (balanitis) along with a smelly, lumpy discharge under the foreskin.

How is esophageal thrush diagnosed?

Esophageal candidiasis, as well as candidiasis of the gastrointestinal or respiratory tract, requires a flexible, tube-like scope—called an endoscope—to visualize tissues beyond the throat. Performed under anesthesia, an endoscopy allows the doctor to examine the extent of the infection and to biopsy tissues that can then be cultured in the lab.

When are blood tests needed to diagnose thrush?

When candidiasis is invasive (spreading to distant organs, typically in severely immunocompromised people), a blood test called the T2Candida panel can be used to detect the type of Candida fungus involved. This blood test is far faster—three to five hours vs. six days—than culturing fluid or tissue samples.

When are imaging tests used to diagnose thrush?

In people with invasive candidiasis, magnetic resonance imaging (MRI) with contrast agents can show changes in tissues of the brain, kidneys, and other organs consistent with the infection. Blood tests and tissue biopsy can further confirm the diagnosis.

What other conditions look like thrush?

Doctors may investigate other causes of thrush-like symptoms if the diagnosis is less than certain. Other conditions with similar symptoms include:

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Article Sources
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  1. Centers for Disease Control and Prevention. Candida infections of the mouth, throat, and esophagus. Updated April 12, 2019.

  2. BMJ Best Practice. Oral candidiasis - Symptoms, diagnosis and treatment. Reviewed August 2019.

  3. National Institute of Diabetes and Digestive and Kidney Diseases. Upper GI Endoscopy. Published July 2017.

  4. Arya NR, Rafiq NB. Candidiasis. In: StatPearls [Internet]. Updated November 20, 2020.

  5. Arendrup MC, Andersen JS, Holten MK, et al. Diagnostic performance of T2Candida among ICU patients with risk factors for invasive candidiasis. Open Forum Infect Dis. 2019;6(5):ofz136. doi:10.1093/ofid/ofz136

  6. Navarathna DH, Roberts DD, Munasinghe J, Lizak MJ. Imaging candida infections in the host. Candida Species. 2019 May;6(5):ofz136. doi:10.1007/978-1-4939-3052-4_6