Lithium is a medication used primarily in the treatment of bipolar disorder and some other mood conditions. It has a narrow therapeutic window, meaning the difference between an effective dose and a toxic dose is relatively small. Regular blood monitoring is a standard and non-negotiable part of lithium therapy.
This test measures the concentration of lithium in your blood, drawn at a specific time point: exactly 12 hours after your last dose. This timing is internationally standardised and allows consistent, comparable results across tests and laboratories. If the timing is off by more than an hour, the result cannot be reliably interpreted, so precision matters.
The target range for lithium maintenance therapy is typically 0.6 to 1.0 mmol/L, while acute treatment of mania may use a slightly higher range of 0.8 to 1.2 mmol/L. Levels below 0.6 mmol/L may be subtherapeutic. Levels above 1.2 mmol/L are concerning, and levels above 1.5 mmol/L can produce serious adverse effects including confusion, tremor, vomiting, diarrhoea, and in severe cases, kidney damage and neurological toxicity.
Many common factors affect lithium levels. Dehydration raises lithium significantly because the kidneys reabsorb more lithium when fluid intake drops. NSAIDs such as ibuprofen, ACE inhibitors, and thiazide diuretics can all increase lithium levels. Low-sodium diets and excessive sweating from heat or exercise also reduce lithium clearance. Your prescribing doctor needs to know about any new medications, supplements, or changes in fluid or salt intake.
Lithium monitoring is typically more frequent when starting the medication or adjusting doses, and at least every six to twelve months once levels are stable. Kidney function and thyroid tests are checked on the same schedule, as lithium can affect both organs over time.
To monitor lithium levels in patients on lithium therapy for bipolar disorder, ensuring therapeutic efficacy and preventing accumulation that can lead to toxicity.
