How Thrush Is Diagnosed

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

In some cases, however, a healthcare provider may need to take a sample from those areas and send it to a laboratory for testing. In more severe cases, when thrush has spread to the esophagus, a diagnostic procedure called endoscopy may be needed.

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At-Home Testing

Although it doesn't always cause symptoms, thrush can cause symptoms such as a white coating on the inside of the 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 has not been scientifically proven to be a reliable test.

Lab Tests

Your healthcare provider may be able to diagnose thrush with a simple visual examination of your mouth and throat.

They may need to take a sample of one of the affected areas in your mouth (also known as lesions) for a microscopic examination. These samples typically involve a gentle, painless scraping.

Throat Culture

In some cases, healthcare providers may use a throat culture to help diagnose thrush. This procedure involves using a cotton swab to collect a sample from the back of the throat. While the swabbing of your throat may be briefly uncomfortable, it’s unlikely to cause pain.

The sample is sent to a laboratory, where it’s placed in a special environment to promote cell growth and analyzed.

Other Tests

Because certain underlying health issues, like diabetes or a weak immune system, can increase the risk of thrush, your healthcare provider may perform further testing to see if you have any risk factors.

Thrush Healthcare Provider Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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Imaging Tests

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

What to Expect

Often done 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 healthcare provider 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 healthcare provider to obtain a close examination of the lining of your upper GI tract.

At this time, your healthcare provider may also perform a biopsy (i.e., the removal of cells or tissue). If you have a biopsy, a pathologist will examine the sampled tissue to check for disease.

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

Some results from your endoscopy may be available right away, and 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 healthcare provider 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 healthcare provider 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, and 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 balanitis (swelling of the penis head) 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, is identified using a flexible, tube-like scope—called an endoscope—to visualize tissues beyond the throat. Performed under anesthesia, an endoscopy allows the healthcare provider 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. Fortunately, invasive fungal infections are extremely uncommon, so this test is rarely indicated.

  • 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?

    Healthcare providers may investigate other causes of thrush-like symptoms if the diagnosis is less than certain.

    Other conditions with similar symptoms include:

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Candida infections of the mouth, throat, and esophagus.

  2. Radfar L, Shea Y, Fischer SH, Sankar V, Leakan RA, Baum BJ, Pillemer SR. Fungal load and candidiasis in Sjögren's syndrome. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003 Sep;96(3):283-7. doi: 10.1016/s1079-2104(03)00224-5

  3. BMJ Best Practice. Oral candidiasis - Symptoms, diagnosis and treatment.

  4. National Institute of Diabetes and Digestive and Kidney Diseases. Upper GI Endoscopy.

  5. Arya NR, Rafiq NB. Candidiasis. In: StatPearls [Internet].

  6. 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

  7. 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

By Cathy Wong
Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.