Introduction – Nitrate-rich beetroot juice (BR) can reduce the oxygen (O2) cost of moderate-intensity exercise and enhance tolerance to severe-intensity exercise (Bailey et al., 2009). A derivative of nitrate (NO3-), nitric oxide, plays a significant role in the regulation of skeletal muscle blood flow, contraction and efficiency. A reduction in blood O2 carrying capacity, as a result of blood donation, reduces the tolerance to severe-intensity exercise (Burnley et al., 2006). The aim of this study was to determine whether BR supplementation alters the haemodynamic response, efficiency and tolerance to cycling exercise post blood donation. Methods – In a randomised and double blind experimental design, 22 recreationally active volunteers performed moderate-intensity and ramp incremental cycle exercise tests prior to and post withdrawal of ~450 mL of whole blood. Before donation, all subjects (n=22) consumed 7 x 70 mL of NO3–depleted beetroot juice shots (~0.04 mmol NO3- per 70mL) as a placebo (PL) in the 48 h preceding the exercise tests. Immediately after blood donation and during the 48 h prior to exercise, subjects consumed 7 shots of either BR (~6.2 mmol NO3- per 70 mL; n=11) or PL (n=11). Blood pressure (BP), plasma NO3- and nitrite (NO2-) concentrations, haemoglobin concentration ([Hb]), haematocrit (Hct) and pulmonary VO2 responses to exercise were measured during each visit to the laboratory. Results – BR supplementation resulted in an increased plasma [NO3-] (PL: 50±14 vs. BR: 845±350 µM; P<0.05) and [NO2-] (PL: 72±21 vs. BR: 619±363 nM; P<0.05) post blood donation. Systolic BP was reduced in BR post blood donation when compared with baseline. [Hb] and Hct decreased significantly from pre to post blood withdrawal, however, no difference was noted between PL and BR. Compared with pre donation, the steady state VO2 during moderate-intensity exercise was ~4% lower post donation in BR only (P<0.05). The ramp test peak power decreased from pre donation (PL: 341±70 vs. BR: 331±68 W) to post donation (PL: 324±69 vs. BR: 322±66 W) in both groups (P<0.05). However, the decrement in performance was less in BR compared with PL (P<0.05). Discussion – Nitrate supplementation reduces the O2 cost of moderate-intensity exercise and lessens the decline in ramp incremental performance after blood donation. The results from this study may have implications for improving functional capacity in conditions where normal blood O2 carrying capacity is impaired.