We have the expertise to give advice on the collection of biomarkers in chronobiological studies, and we offer to analyse several biomarkers in saliva, urine or serum samples in our laboratory. In particular we run Radio-Immuno Assays (RIA) or Enzyme-Immuno assays (ELISA or EIA) for melatonin concentration, 6-sulfatoxy melatonin, and cortisol concentration. For other endocrinology markers, please contact us.


In collaboration with the Faculty of Mathematics and Natural Sciences of the University of Groningen, The Netherlands, we have an endocrinology laboratory and an isotope laboratory available for our analyses. We have highly experienced personnel and we take part in inter-laboratory comparisons.

Biomarker analyis service

We assay melatonin concentration in saliva or plasma, 6-sulfatoxymelatonin in urine, or other biomarkers on request.

In the case of melatonin analysis in saliva, you may:

  • either organize the collection of the saliva samples yourself and send them to us for the analysis (please click ‘request melatonin analysis’ below as soon as you plan to take the samples).
  • or we will organize the collection of the samples and send you the result of the analysis (please click ‘request melatonin analysis’ below and complete the form for a ‘patient package melatonin analysis’).
Request melatonin analysis
  • On request of somnologists or other health professionals, we run single/multiple series of saliva samples for the analysis of Dim Light Melatonin Onset or full 24h-curves of melatonin in patients.
  • We run large batches of samples obtained in clinical or pre-clinical (research) studies for medical institutes or research groups. Please contact us for more information.
  • We do not run a melatonin analysis commissioned by private customers. A single melatonin value is not indicative of any sleep disturbance and the results of a phase marker analysis with the help of melatonin can only be interpreted by an experienced specialist. First consult your doctor if you think a melatonin analysis is worthwile to understand your complaints.
  • Report (pdf) of the values of salivary melatonin concentration in each sample, including a graphical representation of the pattern, the calculated value of DLMO based on 3 pg/ml and 25% of the maximum (if possible) and a short interpretation of the results.
  • Excelfile with salivary melatonin concentration values, including DLMO analysis based on 3 pg/ml or 25% of the maximum (if possible) on request
  • Excelfile with salivary cortisol concentration values