Biomarkers indicating biological age are of significant interest for prevention, diagnosis and monitoring (and the treatment) of age-related diseases. We previously reported an alteration of serum N-glycan profile in old humans using "DNA Sequencer Adapted-Fluorophore Assisted Carbohydrate Electrophoresis" (DSA-FACE). To validate the shift in serum N-glycan profile during ageing, we studied serum N-glycan profiles in different age groups of healthy volunteers, patients with dementia, and patients with Cockayne syndrome, a genetic DNA repair disorder involving neurodegeneration and premature ageing. We found that the log of the ratio of two glycans (NGA2F and NA2F), named GlycoAgeTest, remained steady up to the age of 40. years and thereafter gradually increased to reach its highest level in nonagenarians. Patients with dementia or Cockayne syndrome had a higher GlycoAgeTest level than age-matched healthy individuals. We thus demonstrate that the value of GlycoAgeTest is better than chronological age for estimating the physiological age of a human individual, and that it could be used as an ageing biomarker for healthy humans. Our data indicate that the GlycoAgeTest could be used as a non-invasive surrogate marker for general health, for forecasting disease progression during ageing, and for monitoring the efficacy of anti-ageing food compounds.