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Cortisol nmol/L → µg/dL

Convert cortisol from nmol/L to µg/dL

Sources last checked: 2026-11-03

Cortisol nmol/L → µg/dL

Convert cortisol from nmol/L to µg/dL

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Converts units only; reference ranges depend on the laboratory, the assay and the patient.

Source: AMA Manual of Style, 11th ed. (Oxford Academic) — Units of measure converter, Table 2: Selected laboratory tests and conversion factors.Open

What is the Cortisol nmol/L → µg/dL?

UK and many European endocrine guidelines and laboratories express serum cortisol in nmol/L, while laboratories in Germany, Austria, Turkey and the USA commonly use µg/dL. This converter divides by 27.59 (about × 0.03625), the factor derived from the molar mass of cortisol (362.5 g/mol). The same factor applies to salivary cortisol concentrations.

When to use it

  • Translating a nmol/L cortisol from a European report or protocol into µg/dL
  • Reading US endocrine literature that uses µg/dL
  • Comparing stimulation or suppression test results across laboratories
  • Teaching and exam preparation

When not to use it

  • Patients on prednisolone or hydrocortisone without considering assay cross-reactivity or the drug itself — the conversion cannot separate them
  • 24-hour urinary amounts (nmol/24 h) unless you convert them as amounts, not concentrations
  • Comparing results from immunoassay and LC-MS/MS as if they were interchangeable

How it is calculated

Cortisol (µg/dL) = cortisol (nmol/L) ÷ 27.59

Clinical pearls and limitations

  • Converts units only; reference ranges depend on the laboratory, the assay and the patient.
  • 1 nmol/L ≈ 0.03625 µg/dL; 300 nmol/L ≈ 10.9 µg/dL.
  • Give µg/dL with one decimal.
  • Total cortisol depends on binding proteins; conditions that change corticosteroid-binding globulin or albumin change the total without the same change in free cortisol.
  • Reference ranges and dynamic-test thresholds depend on time of day, assay and guideline; check the source rather than converting a remembered number.

Frequently asked questions

How do I convert cortisol from nmol/L to µg/dL?

Divide by 27.59. For example, 300 nmol/L ÷ 27.59 = 10.9 µg/dL and 50 nmol/L ÷ 27.59 = 1.8 µg/dL.

What is 1 nmol/L of cortisol in µg/dL?

About 0.03625 µg/dL, from cortisol's molar mass of 362.5 g/mol.

Does hydrocortisone show up as cortisol?

Yes. Hydrocortisone is chemically identical to cortisol, so it is measured as cortisol; timing of the last dose matters when reading the result.

Evidence and guidelines

  1. Primary source: AMA Manual of Style, 11th ed. (Oxford Academic) — Units of measure converter, Table 2: Selected laboratory tests and conversion factors.
  2. PubChem compound summary: cortisol (hydrocortisone) (CID 5754), molecular weight 362.5 g/mol.

Have a follow-up question?

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For healthcare professionals and medical students. These tools support, and do not replace, clinical judgement. Always check results against the original source and your local protocols.