The Food and Drug Administration has approved using EPO to maintain between 11 and 12 grams of hemoglobin per deciliter of blood in kidney disease patients.

One-fifth of the 500,000 kidney dialysis patients in the U.S. now receive EPO treatments to maintain their hemoglobin at 13 grams or higher, according to government statistics.

The U.S. study, led by researchers at Harvard Medical School, found an increased risk of serious complications in patients with a hemoglobin level of 13.5 grams, compared to patients with a level of 11.3 grams. The study was paid for by Johnson & Johnson, which markets EPO in the U.S.