What is Lithium?
Lithium has a narrow therapeutic window, and can be toxic if the dose is too high. Therefore, monitoring of Lithium levels is essential for maximising therapeutic effect while preventing toxicity.
Monitoring Requirements in Primary Care
The information below describes the tests required and their frequency for general monitoring of the effects of lithium. More frequent long-term monitoring may be advised by the specialist team in certain circumstances.
Monitoring & Frequency
Monitoring | Frequency |
Plasma lithium level taken 10-14 hours post-dose (as close to 12-hours post-dose as possible) | Every 12 weeks for the first year, then every 6 months (unless otherwise specified by specialist). |
U&Es, (including eGFR)
Calcium (bone profile)
TFTs | Every 6 months (unless otherwise specified by specialist). |
Height, weight, and BMI | Every 6 months (unless otherwise specified by specialist). |
For Bipolar Disorder - blood tests above plus: | |
Blood lipid profile
Fasting blood glucose
HbA1c
LFTs
Cardiovascular status including pulse and BP
Diet, nutritional status and level of physical activity | Annually (see Severe Mental Illness (SMI) for more details of annual review) |
Test Results & Actions
Pregnancy/Family Planning
It is the responsibility of the specialist to provide advice on the need for contraception to male and female patients on initiation. However, both the primary care prescriber and the specialist are responsible for informing patients of the risks and benefits of taking lithium during pregnancy and breastfeeding, throughout the care of the patient.
Patients of child‐bearing potential should be advised to use a reliable form of contraception.
🔗 Further info for HCPs can be found here: https://www.medicinesinpregnancy.org/bumps/monographs/USE-OF-LITHIUM-IN-PREGNANCY/
Significant Medicine Interactions
Care should be taken on initiation, dose adjustment or discontinuation of any interacting medicines, as the onset and degree of the interaction can vary. Discuss with specialist team and note that additional lithium monitoring is likely to be indicated, with doses adjusted accordingly.
- elderly patients
- patients with renal impairment
- patients with altered laboratory parameters
- those with poor symptom control or adherence
- those using concurrent interacting medicines
- if most recent 12-hour plasma lithium level is at the threshold of target range
Consider additional monitoring whenever there is a change in the patient’s circumstances, e.g. intercurrent illness.
Due to the narrow therapeutic window of lithium, toxicity is a serious concern.
Excluding excessive ingestion, toxicity most commonly arises from a reduced elimination of lithium by the kidneys. Lithium toxicity can itself impair renal function, so rapid escalations in plasma lithium levels can occur.
Toxicity usually occurs at levels >1.5 mmol/L. However, it can also occur at lower levels, even within the ‘therapeutic range’, in susceptible patients (e.g., the elderly, patients with renal impairment, dehydrated patients, etc.).
If lithium toxicity is suspected → perform urgent lithium level immediately and seek specialist advice. Withhold lithium if there are features of toxicity.
If lithium level ≥2.0mmol/L → consider sending patient to A&E, based on clinical presentation, and inform specialist team.
Patient Advice
The patient should be counselled by the specialist upon initiation of treatment of the following information. However, as some of these instructions involve the GP directly, it is also prudent to remind the patient of this information when necessary.
The patient should be advised to report any of the following signs or symptoms to their GP without delay:
- signs of lithium toxicity (see box above)
- signs of hypothyroidism (e.g. fatigue, cold intolerance, weight gain, constipation and depression)
- signs of renal dysfunction (including polyuria and polydipsia)
- symptoms of benign intracranial hypertension (persistent headache and visual disturbance)