Heavy metal poisoning refers to when excessive exposure to a heavy metal affects the normal function of the body. Examples of heavy metals that can cause toxicity include lead, mercury, arsenic, cadmium, and chromium. Exposure may occur through the diet, from medications, from the environment, or in the course of work or play. Heavy metals can enter the body through the skin, or by inhalation or ingestion. Toxicity can result from sudden, severe exposure, or from chronic exposure over time. Symptoms can vary depending on the metal involved, the amount absorbed, and the age of the person exposed. For example, young children are more susceptible to the effects of lead exposure because they absorb more compared with adults and their brains are still developing. Nausea, vomiting, diarrhea, and abdominal pain are common symptoms of acute metal ingestion. Chronic exposure may cause various symptoms resulting from damage to body organs, and may increase the risk of cancer. Treatment depends on the circumstances of the exposure.

Signs and symptoms of heavy metal poisoning vary depending on the type and amount of metal involved. Fetuses and young children are at the highest risk for severe and long term health consequences from heavy metal exposure. Early symptoms may be missed because they are often nonspecific. Excessive exposure and damage to several organs can occur even if a person has no symptoms. Some signs and symptoms of metal poisoning may include:

• Abdominal pain, nausea, vomiting, and diarrhea (the hallmark symptoms with most cases of acute metal ingestion)
• Dehydration
• Heart abnormalities such as cardiomyopathy or abnormal heart beat (dysrhythmia)
• Nervous system symptoms (e.g. numbness, tingling of hands and feet, and weakness)
• Anemia (a classic symptom of chronic metal exposure)
• Kidney damage
• Liver damage
• Lung irritation, or fluid accumulation (edema)
• Brain dysfunction such as memory loss
• Horizontal lines on the nails
• Changes in behavior
• Malformed bones in children, or weakened bones
• Miscarriage or premature labor in pregnant women

Diagnosing heavy metal poisoning can be difficult, as it relies on having a known exposure and positive results on approved tests. Heavy metal poisoning is often first suspected based on a patient's history and/or symptoms consistent with excessive exposure. The following tests may help make the diagnosis of heavy metal toxicity, or help determine how severe the exposure is:

• Complete blood count (CBC) with peripheral smear
• Renal (kidney) function tests
• Urine analysis (looking for protein in the urine)
• Liver function studies
• Imaging studies such as abdominal radiographs
• Electrocardiogram

Testing is available in panels (where multiple exposures are tested) or by individual metal. The testing performed depends on the person's symptoms and suspected exposure. Metals more commonly tested for include lead, mercury, arsenic, cadmium, and chromium. Metals less commonly tested for include aluminum, beryllium, cobalt, copper, iron, manganese, nickel, platinum, selenium, silicon, silver, and thallium.

For further information on testing for heavy metal poisoning, visit Lab Tests Online, a website developed by the American Association for Clinical Chemistry. To view a list of conditions with signs symptoms that overlap with those of heavy metal poisoning, visit Medscape's website.