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.
Your result report includes the reference range that applies to your sample. Your prescriber sets your individual target range and can explain what your number means for you. A level below that target range may be subtherapeutic, and a level above it 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, checking whether the level sits within the prescriber's target range.
