Chromium is a metallic element (atomic number: 24, atomic mass: 51.99), it is a mineral essential in the action of insulin and is present in very small quantities in many enzymes. Chromium is also present in many foods such as brewers' yeast, seeds, peanuts, wheat germ and skimmed milk. Chromium Cr-51 is an isotope of chromium that is observationally stable. When intravenously administered, it is used as a diagnostic radiopharmaceutical agent to determine the red blood cell volume or mass, study the red blood cell survival time and evaluate blood loss. Chromium 51 is also used for labeling platelets, and for the diagnosis of gastrointestinal bleeding.

Nearly 60 years ago, chromium, as the trivalent ion, was proposed to be an essential element, but the results of new studies indicate that chromium currently can only be considered pharmacologically active and not an essential element. Chromium is a mineral that humans need in very small quantities. Good sources include broccoli, liver, and brewers' yeast. Taking chromium by mouth is effective for preventing chromium deficiency. It is also taken by mouth for depression, Turner's syndrome, polycystic ovary syndrome (PCOS), lowering "bad" cholesterol, raising "good" cholesterol in people taking heart medications called beta blockers, obesity, metabolic syndrome, heart attack, schizophrenia, bipolar disorder, binge eating disorder, and a disease called reactive hypoglycemia. Chromium has been marketed as an agent to reduce body mass and develop muscle; however, such marketing claims are no longer allowed in the United States because they are not supported by experiments. Trivalent chromium has also been proposed as a therapeutic agent to increase insulin sensitivity and affect lipid metabolism. Although effective in certain rodent models, beneficial effects in humans have not been unequivocally established.