Cortisol µg/dL → nmol/L
Convert cortisol from µg/dL to nmol/L
Sources last checked: 2026-11-03
Cortisol µg/dL → nmol/L
Convert cortisol from µg/dL to nmol/L
Converts units only; reference ranges depend on the laboratory, the assay and the patient.
What is the Cortisol µg/dL → nmol/L?
Serum cortisol is reported in µg/dL in Germany, Austria, Turkey and the USA and in nmol/L in the UK and many other European countries, where most endocrine guidelines are also written in nmol/L. This converter multiplies by 27.59, which follows from the molar mass of cortisol (hydrocortisone, 362.5 g/mol). It converts total cortisol; free cortisol is a separate measurement.
When to use it
- Comparing a µg/dL cortisol with European endocrine literature or test protocols in nmol/L
- Interpreting a short Synacthen (ACTH stimulation) or dexamethasone suppression test against a source written in nmol/L
- Comparing results from different laboratories
- Exam questions on adrenal insufficiency and Cushing's syndrome
When not to use it
- Urinary free cortisol reported per 24 h — convert the concentration only after checking whether the report gives an amount (nmol/24 h, µg/24 h) or a concentration
- Cortisone or 11-deoxycortisol, which are different steroids with different molar masses
- Transferring a cut-off between assays: the conversion is exact, but thresholds are assay-specific
How it is calculated
Cortisol (nmol/L) = cortisol (µg/dL) × 27.59
Clinical pearls and limitations
- Converts units only; reference ranges depend on the laboratory, the assay and the patient.
- 1 µg/dL = 27.59 nmol/L; 12 µg/dL ≈ 331 nmol/L.
- Total cortisol rises with corticosteroid-binding globulin (e.g. oral oestrogens, pregnancy) and falls with low binding proteins (e.g. critical illness, nephrotic syndrome), without the same change in free cortisol.
- Immunoassays can cross-react with prednisolone and other steroids; LC-MS/MS is more specific and may give lower values.
- Cortisol follows a circadian rhythm; reference ranges and test thresholds depend on sampling time, assay and guideline.
Frequently asked questions
How do I convert cortisol from µg/dL to nmol/L?
Multiply by 27.59. For example, 12 µg/dL × 27.59 = 331 nmol/L and 3 µg/dL × 27.59 = 83 nmol/L.
Why is the cortisol factor 27.59?
Cortisol has a molar mass of 362.5 g/mol. 1 µg/dL is 10 µg/L, and 10 000 ÷ 362.5 = 27.59 nmol/L.
Can I use a nmol/L cut-off from a UK paper on my µg/dL result?
Convert the unit, but also check the assay: cortisol immunoassays differ systematically, and many protocols now give assay-specific thresholds.
Evidence and guidelines
Have a follow-up question?
Medelix answers clinical questions from current guidelines and studies — every statement with its source.
Related calculators
Embed this calculatorFree to use on your website, intranet or teaching page. Copy the code below.
<iframe src="https://medelix.ai/en/embed/cortisol-ugdl-to-nmol" title="Cortisol µg/dL → nmol/L – Medelix" width="100%" height="620" style="border:0;max-width:720px" loading="lazy"></iframe>
<p><a href="https://medelix.ai/en/calculators/cortisol-ug-dl-to-nmol-l">Cortisol µg/dL → nmol/L calculator by Medelix</a></p>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.