What is the most common risk factor for lithium toxicity?

Dehydration and low sodium levels are the most common risk factors for lithium toxicity because lithium is a medication that is primarily excreted through the kidneys. Its serum levels are closely linked to the body's sodium balance and hydration status. When a patient is dehydrated or has low sodium, the kidneys may reabsorb more lithium, leading to increased serum levels and a higher risk of toxicity.

This risk is especially notable because low sodium levels (hyponatremia) can occur due to various factors, including diuretic use, gastrointestinal losses, or inadequate fluid intake. In a dehydrated state or with hyponatremia, the body's ability to manage lithium levels is compromised, making toxicity more likely.

Other options, while they can contribute to lithium toxicity, do not pose as immediate or common a risk as dehydration and low sodium levels. For instance, renal failure can lead to increased lithium levels, but many patients with renal issues are monitored closely for this reason. Excessive caffeine intake and concurrent use of diuretics can also play a role in affecting lithium levels but generally do not have as direct and prominent an effect on hydration and sodium balance as dehydration does. Therefore, ensuring adequate hydration and normal sodium levels is crucial in preventing