What factors affect lithium levels in biological samples?

Factors such as excessive intake and impaired excretion affect lithium levels in biological samples. If lithium is taken inadvertently or intentionally, it may result in acute or acute-on-chronic overdose toxicity. Excessive intake may also occur from alterations in dosage for the patient previously taking lithium. Impaired excretion may also occur due to various factors (e.g. vomiting, excessive exercise, low sodium diet, and water restriction). This causes the stimulation of lithium reabsorption in the kidneys and affects the levels being measured in the blood, resulting in an increased lithium concentration. Drugs depleting the glomerular filtration may also result in chronic toxicity.