Also known as: often referred to by the brand name (see MedlinePlus Drug Information)
Name: Lithium
Related tests: Creatinine, T4, TSH
Why measure it?
To determine the concentration of lithium in the blood in order to maintain a therapeutic level or to detect lithium toxicity.
When to measure it?
At regular intervals to monitor lithium levels, and as needed to detect low or toxic concentrations.
Sample required?
A blood sample taken from a vein in the arm.
What is being measured?
The test measures the amount of lithium in the blood. Lithium is a medicine used to treat bipolar disorder. Bipolar disorder is a mental health condition characterised by cycles of depression and mania. These cycles may be as short as a few days or weeks or may last months or years. During a depressive episode, people may feel sad, hopeless and worthless and lose interest in everyday activities. They may be tired and have difficulty sleeping, may lose or gain weight, have difficulty concentrating and think about suicide. During a manic episode, people may be euphoric or irritable, have a lot of energy and grandiose ideas, use poor judgement and take risks. Sometimes patients have mixed episodes with features of both mania and depression. Bipolar disorder can affect both adults and children.
Lithium is prescribed to even out the moods of people with bipolar disorder and is sometimes prescribed for patients with depression who do not respond well to other treatments. Lithium can take weeks to months to affect a person’s mood. Doses of the medicine are adjusted until a steady concentration in the blood is reached. The amount of medicine needed to reach this steady state varies from person to person and can be affected by the person’s age, general health and other treatments they are taking. Lithium levels must be kept within a narrow therapeutic range. Too little and the medicine will not be effective; too much and patients will have symptoms of lithium toxicity, such as nausea, vomiting, diarrhoea, confusion and tremors. Extremely high levels can lead to stupor and seizures and can be fatal.
How is it used?
When is it requested?
What does the result mean?
Is there anything else I should know?
How is it used?
The lithium test is requested to measure and monitor the amount of lithium in the blood to determine whether concentrations of the medicine are within the therapeutic range. When a patient first starts taking lithium, the test may be requested every few days to help adjust the dose to the desired blood level. The test may be requested at regular intervals or as needed to monitor blood concentrations. One or more lithium tests may be requested if a patient starts taking additional treatments (to judge their effect on lithium levels) and may be requested if the doctor suspects toxicity.
When is it requested?
Lithium is measured frequently when a patient is starting lithium treatment or restarting it after a break. Once steady blood concentrations within the therapeutic range have been reached, lithium can be monitored at regular intervals to make sure it stays within this range.
The test may be requested when a patient’s condition does not appear to be responding to lithium, to determine whether concentrations are too low, whether the treatment is ineffective and/or whether the patient is taking lithium regularly. It may also be requested when a patient has worrying side effects and/or shows symptoms that the doctor suspects may be due to toxicity.
Patients should tell their doctor the time the sample was collected. Blood lithium levels are generally measured 12-18 hours after the last dose. Since dosing times vary and some formulations release lithium slowly, sample collection details may vary.
What does the result mean?
The therapeutic range for lithium has been set at 0.6-1.2 mmol/L. Within this range, most people respond to the medicine without symptoms of toxicity. However, response and side effects vary from person to person. Some bipolar conditions are not adequately treated at the lower end of the therapeutic range, and some people may have excessive side effects at the upper end. Patients should work closely with their doctor to find the dose and concentration that work best for them.
In general, when lithium results are within the therapeutic range, the patient’s bipolar disorder is well controlled and they are not having significant side effects, doctor and patient are satisfied, and the dose of lithium the patient is receiving is considered adequate. If the patient is below the therapeutic range, they are probably not receiving adequate treatment. If they are above the therapeutic range and/or having significant side effects with the current dose, they are probably taking too much medicine. However, patients should not reduce or stop their treatment without consulting their doctor, as this can make their bipolar symptoms worse. Dosing decisions and adjustments must be assessed case by case.
Is there anything else I should know?
Lithium is excreted mainly by the kidneys. Long-term use of lithium leads to a decline in kidney function. Patients with kidney disease may have raised lithium levels because of reduced elimination. Doctors will monitor kidney function throughout treatment with tests such as BUN and creatinine.
Patients taking lithium can develop hypothyroidism (reduced thyroid function). Doctors regularly monitor the patient’s thyroid function with TSH and/or T4.
Women who take lithium during pregnancy have an increased risk of the baby developing a rare heart valve defect. Women who want to become pregnant should discuss this with their doctor.
A variety of prescription and over-the-counter medicines and supplements can raise, lower or interfere with blood lithium concentrations. Medicines that can raise lithium in the body include anti-inflammatories such as ibuprofen and naproxen and diuretics such as hydrochlorothiazide and furosemide. Medicines that can increase the side effects of lithium include antipsychotics such as clozapine and olanzapine, blood pressure medicines such as calcium channel blockers and ACE inhibitors, and antiepileptics such as carbamazepine. Medicines that can lower lithium include theophylline and caffeine.
Lithium levels and side effects can increase with the loss of salt and water from the body, as can happen with a salt-free diet, excessive sweating or an illness causing vomiting and diarrhoea
1. How long will I need to stay on lithium?
2. Who requests the lithium test?
3. Can I test my lithium level at home?
1. How long will I need to stay on lithium?
Lithium is usually taken every day for the rest of the patient’s life. Bipolar disorder can be controlled but not cured.
2. Who requests the lithium test?
It may be monitored by your doctor but may also be requested and monitored by a mental health specialist.
3. Can I test my lithium level at home?
No, it requires specialised equipment. Most blood samples are taken from a vein in the arm and tested in a laboratory. However, the FDA has recently approved a test that can be carried out in the doctor’s surgery (it requires blood from a finger). At present this test is not widely used, but it may become available in the near future.