Clinical trial data for the efficacy of glucosamine in OA are conflicting. Reportedly, Rotta-manufactured glucosamine products are more likely to be effective, and a possible explanation is greater bioavailability than other brands. Specifically, the aim was to compare the steady-state pharmacokinetics of Rotta- and non-Rotta-manufactured glucosamine products in healthy volunteers and examine the interindividual variability.In a crossover design, healthy adult participants ingested 1500 mg/day of a Rotta (DONA powder sachets; imported by Mylan Health, Carole Park, QLD, Australia) and a non-Rotta (glucosamine sulphate 1500 mg one-a-day tablet; Blackmores, Warriewood, NSW, Australia) glucosamine product/brand individually for 6 days. Blood samples were collected immediately before and for 12 h after the ingestion of the last dose of each brand and analysed to determine plasma levels of glucosamine. The pharmacokinetic parameters at steady state [including the minimum (Css min) and maximum (Css max) plasma concentration of glucosamine, time to reach Css max post-dosing (Tss max) and area under the plasma concentration vs time curve (AUCss 0-12)] for each brand were calculated and statistically compared.Fourteen participants [mean age 35.5 years (s.d. 8.8)] were recruited (64.2% males). No significant differences were observed in the pharmacokinetic parameters between the two brands. However, for both brands, the coefficient of variation for Css min, Tss max and AUCss 0-12 exceeded 20%, indicating considerable differences in the parameters between participants. No significant association of the pharmacokinetic parameters was observed with various dosing- and participant-related variables.Substantial interindividual differences in the absorption and elimination of glucosamine could be a cause of variable clinical outcomes in OA.The study was registered with the Australian New Zealand Clinical Trials Registry (http://www.ANZCTR.org.au/ACTRN12618000699268p.aspx), number ACTRN12618000699268p.