Investigations in acne

Author: Reviewed and updated by Dr Amanda Oakley Dermatologist, Hamilton, New Zealand and Vanessa Ngan, Staff Writer, February 2014.

No tests are necessary for most patients with acne. Tests may be requested to look for infection, to investigate the cause of the disease, or to monitor treatment.

Tests for bacteria

Although bacteria, especially Cutibacterium acnes, are involved in the development of acne, they are a normal part of the skin flora and can be detected in people with or without acne lesions.

Occasionally it is wise to obtain a swab and/or scraping from an acne spot, or acne-like pustule, for microbiological examination and culture. This is because acne can resemble infections, including:

Hormone tests

Some women may be advised to have blood tests to measure hormone levels. The reasons include:

These hormone tests are best taken between 8:00 and 10:00 am during the first half of the menstrual cycle. They may include:

  • Testosterone
  • Sex hormone binding globulin (SHBG)
  • Free androgen index (FAI)
  • Dehydroepiandrosterone sulfate (DHEAS)
  • 17-hydroxyprogesterone
  • Synacthen test of adrenal stimulation by adrenocorticotrophic hormone (ACTH)
  • Luteinising hormone (LH) and follicular stimulating hormone (FSH)
  • Prolactin
  • Cortisol
  • Dexamethasone suppression test


A pelvic ultrasound scan is usually very good at excluding ovarian cysts and tumours on the ovary and adrenal gland. X-rays, computed tomography (CT) scans or magnetic resonance imaging (MRI) may also be arranged if there is suspicion of tumour.

Tests to monitor treatment

Blood tests may be performed to monitor the safety of treatment:

  • Full blood count (especially if the patient is unwell)
  • Liver function in those on antibiotics or isotretinoin
  • Fasting lipids (cholesterol and triglyceride) in those on isotretinoin
  • Beta human chorionic gonadotrophin or HCG (pregnancy test) in those on isotretinoin

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