URL of this page: https://medlineplus.gov/lab-tests/differential-diagnosis/

Differential Diagnosis

What is a differential diagnosis?

Not every health disorder can be diagnosed with a simple lab test. Many conditions cause similar symptoms. For example, many infections cause fever, headaches, and fatigue. Many mental health disorders cause sadness, anxiety, and sleep problems.

A differential diagnosis looks at the possible disorders that could be causing your symptoms. It often involves several tests. These tests can rule out conditions and/or determine if you need more testing.

How is it used?

A differential diagnosis is used to help diagnose physical or mental health disorders that cause similar symptoms.

How will my provider make a differential diagnosis?

Most differential diagnoses include a physical exam and a health history. During a health history, you'll be asked about your symptoms, lifestyle, and previous health problems. You'll also be asked about your family's health problems. Your provider may also order lab tests for different diseases. Lab tests are often done on blood or urine.

If a mental health disorder is suspected, you may get a mental health screening. In a mental health screening, you will be asked questions about your feelings and mood.

The exact tests and procedures will depend on your symptoms.

For example, you may see your health care provider because you have a skin rash. Rashes can be caused by a wide variety of conditions. Causes can range from mild allergies to life-threatening infections. To make a differential diagnosis of a rash, your provider may:

  • Do a thorough exam of your skin
  • Ask you if you been exposed to any new foods, plants, or other substances that could cause an allergy
  • Ask about recent infections or other diseases
  • Consult medical text books to compare your how your rash looks to rashes in other conditions
  • Perform blood and/or skin tests

These steps can help your provider narrow down the choices of what is causing your rash.

What do my results mean?

Your results may include information about conditions you don't have. It's important to learn this information to narrow down the possibilities of potential disorders. The results may also help your provider figure out which additional tests you need. It can also help determine which treatments might help you.

Is there anything else I need to know about a differential diagnosis?

A differential diagnosis can take a lot of time. But it can help make sure you get the right diagnosis and treatment.


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The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.