INTRODUCTION: Extended intervals between sample collection and analyses render athlete's whole-blood specimens collected in the field for antidoping purposes susceptible to storage degradation. The aim of this study was to characterize the stability of key blood variables under different storage durations and temperatures. METHODS: We evaluated stability of full blood count indices (plus reticulocytes) in individual tubes left undisturbed during 36, 48, 72, 96, 120, 144 and 168 h of storage at approximately 4, 6 and 12 °C. Samples were measured on a Sysmex XT-2000i instrument. RESULTS: The two key variables in the context of antidoping (haemoglobin concentration, reticulocytes) were stable for at least 168 h, except under 12 °C (stable 48 h only). Volume-dependent variables changed in a predictable manner that enabled a nomogram to be generated to predict original values provided storage duration and temperature were known. CONCLUSION: Key blood results can be relied upon for at least 7 days if storage temperature is kept at 4-6 °C.