In supplemental amounts (typically 50–300 mcg per day), chromium has not been found to cause toxicity in humans. While there are a few reports of people developing medical problems while taking chromium, a cause-effect relationship was not proven. One study suggested that chromium in very high concentrations in a test tube could cause chromosomal mutations in ovarian cells of hamsters.^17,18 Chromium picolinate can be altered by antioxidants or hydrogen peroxide in the body to a form that could itself create free radical damage.¹⁹ In theory, these changes could increase the risk of cancer, but so far, chromium intake has not been linked to increased incidence of cancer in humans.²⁰

One report of severe illness (including liver and kidney damage) occurring in a person who was taking 1,000 mcg of chromium per day has been reported.²¹ However, chromium supplementation was not proven to be the cause of these problems. Another source claimed that there have been reports of mild heart rhythm abnormalities with excessive chromium ingestion.²² However, no published evidence supports this assertion.

Three single, unrelated cases of toxicity have been reported from use of chromium picolinate. A case of kidney failure appeared after taking 600 mcg per day for six weeks.²³ A case of anemia, liver dysfunction, and other problems appeared after four to five months of 1,200–2,400 mcg per day.²¹ A case of a muscle disease known as rhabdomyolysis appeared in a body builder who took 1200 mcg over 48 hours.²⁵ Whether these problems were caused by chromium picolinate or, if so, whether other forms of chromium might have the same effects at these high amounts remains unclear. No one should take more than 300 mcg per day of chromium without the supervision of a doctor.