Excessive cobalt in the blood is considerably more common than a deficiency, however. Patients may come into contact with this material during the course of industrial work such as tungsten carbide fabrication, glass production or pigment manufacturing. Cobalt contamination of the environment may also produce inappropriately high serum cobalt levels, as can exposure to some leaking batteries, pigments, dyes or metals. Symptoms of cobalt poisoning involve nausea and vomiting or rashes on the skin. Long-term exposure can produce deterioration of the heart muscle, nerve problems, blood thickening or thyroid conditions.

Patients who are concerned they may have been exposed to cobalt may choose to have a blood test to check their serum levels of this mineral. This test doesn't require fasting beforehand and should show levels of less than 1 nanogram per milliliter. People with higher levels could have environmental or occupational exposure problems that may result in future health problems. Levels of 5 ng/mL indicate major exposure and possible poisoning. In people who have cobalt-based implants, levels of 10 ng/mL or greater indicate a problem that needs attention quickly.