Unfair athletes seek ways to stimulate erythropoiesis, because the mass of haemoglobin is a critical factor in aerobic sports. Here, the potential misuse of cobalt deserves special attention. Cobalt ions (Co2+) stabilize the hypoxia‐inducible transcription factors (HIFs) that increase the expression of the erythropoietin (Epo) gene. Co2+ is orally active, easy to obtain, and inexpensive. However, its intake can bear risks to health. To elaborate this issue, a review of the pertinent literature was retrieved by a search with the keywords ‘anaemia’, ‘cobalt’, ‘cobalt chloride’, ‘erythropoiesis’, ‘erythropoietin’, ‘Epo’, ‘side‐effects’ and ‘treatment’, amongst others. In earlier years, cobalt chloride was administered at daily doses of 25 to 300 mg for use as an anti‐anaemic agent. Co2+ therapy proved effective in stimulating erythropoiesis in both non‐renal and renal anaemia, yet there were also serious medical adverse effects. The intake of inorganic cobalt can cause severe organ damage, concerning primarily the gastrointestinal tract, the thyroid, the heart and the sensory systems. These insights should keep athletes off taking Co2+ to stimulate erythropoiesis. Copyright © 2013 John Wiley & Sons, Ltd.