From the Guidelines
To assess whether a new tremor could be related to lithium toxicity, blood should be collected as a "lithium level" or "serum lithium concentration" test, ideally 12 hours after the last dose (trough level), and additional tests such as kidney function, electrolytes, thyroid function, and complete blood count should be performed regularly, as recommended by clinical guidelines 1. When collecting bloodwork to evaluate lithium toxicity, it is crucial to consider the timing of the sample collection, as lithium levels can fluctuate throughout the day based on dosing.
- The sample should be drawn in the morning before the patient takes their morning dose of lithium, using a standard chemistry tube (red or gold top) for collection.
- The therapeutic range for lithium is generally 0.6-1.2 mEq/L, with toxicity often occurring above 1.5 mEq/L, as noted in the context of treating central disorders of hypersomnolence 1.
- Additional bloodwork should include kidney function tests (BUN, creatinine), electrolytes (particularly sodium), thyroid function tests, and a complete blood count, as these can affect lithium levels or be affected by lithium, and regular monitoring is necessary to balance the desirable and undesirable effects of lithium therapy 1.
- Symptoms of lithium toxicity, such as tremor, nausea, diarrhea, slurred speech, confusion, or ataxia, should be monitored closely, especially in elderly patients or those with decreased kidney function, where toxicity can occur even within the therapeutic range.
- Regular monitoring of serum lithium concentrations, ideally twice per week during the acute phase and until the serum concentrations and clinical condition of the patient have been stabilized, is essential for safe lithium therapy 1.
From the FDA Drug Label
Blood samples for serum lithium determination should be drawn immediately prior to the next dose when lithium concentrations are relatively stable (i.e., 8-12 hours after the previous dose). To assess whether a new tremor could be related to lithium toxicity, bloodwork should be collected immediately prior to the next dose, when lithium concentrations are relatively stable, which is typically 8-12 hours after the previous dose 2.
- This allows for an accurate measurement of serum lithium levels, which is essential in evaluating potential lithium toxicity.
- Clinical evaluation is also necessary, as total reliance must not be placed on serum levels alone 2.
From the Research
Bloodwork Collection for Assessing Lithium Toxicity
To assess whether a new tremor could be related to lithium toxicity, bloodwork collection is crucial. The following points highlight the key aspects of bloodwork collection:
- Serum lithium level is a necessary component of blood examination when lithium tremor has developed 3
- Monitoring serum lithium concentrations is essential to achieve optimal efficacy at the lowest possible concentrations and minimize renal side effects 4
- Serum creatinine levels should be monitored at least on a yearly basis to assess renal function 4
- Blood examination can help differentiate lithium tremor from other conditions, such as metabolic abnormalities, benign essential tremor, Parkinson's disease, and lithium toxicity 3
Key Considerations
When collecting bloodwork to assess lithium toxicity, consider the following:
- Severe tremor may be a sign of lithium toxicity, and patients should be evaluated for lithium tremor on a regular basis 5
- Lithium serum levels can contribute to complications such as acute kidney injury (AKI) and nephrotic syndrome (NS) 6
- The underlying pathology of lithium-induced NS with AKI is mainly minimal change disease (MCD), which is quickly reversible upon drug withdrawal 6