Type-2 diabetes mellitus (T2DM) is associated with a reduction of butyrate-producing gut bacteria. d-allulose and erythritol are low-no-calorie sweeteners (LNCS) used as sugar substitutes to reduce high free sugar intakes associated with non-communicable diseases, including T2DM. This is the first study to investigate the impact of representative and physiologically relevant doses of d-allulose and erythritol on the human gut microbiota of T2DM ( n = 6) and co-living healthy adults ( n = 6). Using the clinically predictive ex vivo SIFR® technology, d-allulose and erythritol were shown to significantly increase butyrate production 24-48 h after treatment and significantly increased the abundance of particular microbial families or species in both healthy individuals and those with T2DM compared to the no-substrate control (NSC). d-Allulose significantly increased the abundance of Anaerostipes hadrus and Lachnospiraceae_unclassified_species ( u _ s) at 48 h in healthy adults and adults with T2DM compared to the NSC. Erythritol significantly increased the abundance of Eubacteriaceae and Barnesiellaceae families at 48 h in healthy adults and adults with T2DM but had no significant effects on microbial species compared to the NSC. d-Allulose resulted in a larger increase in butyrate between 6-24 h whereas erythritol resulted in a larger increased butyrate between 24-48 h. The findings suggest prebiotic potential of d-allulose and erythritol worth of investigation in human clinical trials, as blending d-allulose and erythritol could be a promising strategy to reduce free sugar intakes and increase butyrate production in both healthy and T2DM individuals, resulting in beneficial effects on glycemic control.