Aluminum

A metal with no biological role, measured mainly where kidney function is impaired or dialysis is involved.

Healthy kidneys clear it efficiently, so it only accumulates when they cannot -- which is why this is a kidney-context test.

Contamination from tubes, needles and even the water used in processing is a real problem, so a mildly raised value is repeated in a dedicated trace-element tube before it is believed. Antacids are a large and easily missed source.

Worth discussing a raised value together with kidney function.