Which lab tests are useful to exclude medical illnesses that may present as major depressive disorder (clinical depression)?

Updated: Aug 06, 2020
  • Author: Jerry L Halverson, MD; Chief Editor: David Bienenfeld, MD  more...
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Depression is a clinical diagnosis, based on the history and physical findings. No diagnostic laboratory tests are available to diagnose major depressive disorder, but focused laboratory studies may be useful to exclude potential medical illnesses that may present as major depressive disorder. These laboratory studies might include the following:

  • Complete blood cell (CBC) count

  • Thyroid-stimulating hormone (TSH)

  • Vitamin B-12

  • Rapid plasma reagin (RPR)

  • HIV test

  • Electrolytes, including calcium, phosphate, and magnesium levels

  • Blood urea nitrogen (BUN) and creatinine

  • Liver function tests (LFTs)

  • Blood alcohol level

  • Blood and urine toxicology screen

  • Dexamethasone suppression test (Cushing disease, but also positive in depression)

  • Cosyntropin (ACTH) stimulation test (Addison disease)

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