Methylglyoxal in New Zealand mānuka honey has been shown to originate from dihydroxyacetone, which is present in the nectar of mānuka flowers in varying amounts. Mānuka honey, which was freshly produced by bees, contained low levels of methylglyoxal and high levels of dihydroxyacetone. Storage of these honeys at 37 °C led to a decrease in the dihydroxyacetone content and a related increase in methylglyoxal. Addition of dihydroxyacetone to clover honey followed by incubation resulted in methylglyoxal levels similar to those found in mānuka honey. Nectar washed from mānuka flowers contained high levels of dihydroxyacetone and no detectable methylglyoxal.