To measure lithium levels in the blood in order to determine the therapeutic level when just starting lithium medication; to maintain the therapeutic level or to determine lithium toxicity
When beginning treatment with lithium as the dose is adjusted to achieve therapeutic blood levels; at regular intervals to monitor lithium levels; as needed to detect sub-therapeutic levels or high (toxic) concentrations
A blood sample drawn from a vein in your arm
No test preparation is needed. However, timing of the sample collection may affect results. Generally, lithium blood levels are performed 12 hours after the last dose (also known as a "trough" level). Tell the person who draws your blood when you took your last dose so that the results can be interpreted correctly.
Lithium is a drug used as an antipsychotic in the treatment of bipolar disorder. Occasionally, it can be used in other disorders to augment an antidepressant that does not adequately treat a depression. This test measures the amount of lithium in the blood.
Bipolar disorder is a mental condition characterized by alternating periods of depression and mania. These periods may be as short as a few days or weeks or as long as months or years. During a depressive episode, those affected may feel sad, hopeless, worthless, and lose interest in daily activities. They may be fatigued but have trouble sleeping, experience weight loss or gain, have difficulty concentrating, and have thoughts of suicide. During a manic episode, those affected may be euphoric, irritable, have high energy and grandiose ideas, use poor judgment, and participate in risky behaviors. Sometimes affected people will have mixed episodes with aspects of both mania and depression. Bipolar disorder can affect both adults and children.
Lithium is prescribed to stabilize the mood swings of a person with bipolar disorder. It is often called a "mood stabilizer" and is sometimes prescribed for people with depression who are not responding well to other medications. Less commonly, lithium may be prescribed to prevent schizoaffective disorder and cluster headaches.
Because lithium is a relatively slow-acting drug, its effect on mood may take several weeks. Dosages of the drug are adjusted until blood concentrations are within a therapeutic range—the blood level range that achieves the desired effect and treats an individual's bipolar disorder. The actual amount of drug that it will take to reach this steady state will vary from person to person and may be affected by a person's age, general state of health, and other medications that they are taking.
Lithium levels are monitored on a regular basis because blood levels must be maintained within a narrow therapeutic range. Too little and the medication will not be effective; too much and symptoms associated with lithium toxicity may develop.
How is it used?
The lithium test is used to measure and monitor the amount of lithium in the blood so that a healthcare practitioner can determine whether the drug blood concentration is within the range that will adequately treat an individual's bipolar disorder (therapeutic range). The test may be used to measure blood levels every few days when a person first begins taking lithium to help adjust the dose and reach the desired blood level and may also be used at regular intervals or as needed to monitor blood concentrations. If a person starts taking additional medications, a healthcare practitioner may order one or more lithium tests to judge their effect, if any, on lithium levels. Lithium tests may also be ordered if toxicity is suspected.
When is it ordered?
Lithium is ordered frequently when a person is starting lithium treatment. After a person has stable blood concentrations in the therapeutic range, a healthcare practitioner may order lithium tests at regular intervals to ensure that drug levels remain in this range.
The test may be ordered when a person's condition does not appear to be responding to lithium to determine whether concentrations are too low, the medication is ineffective, and/or to determine if the person is complying with therapy (taking the lithium regularly). It may also be ordered when someone experiences a troublesome level of side effects and/or exhibits symptoms that the healthcare practitioner suspects may be due to toxicity, such as:
- Drowsiness, lack of energy
- Muscle weakness
- Lack of coordination
- Slurred speech
- Nausea, vomiting and/or diarrhea
- Irregular tremors or shaking
Extremely high levels can lead to stupor, seizures, renal failure, and death.
Blood samples for lithium levels are generally drawn 12 hours after the last dose. Since dosage timing varies and some formulations are time-released, collection specifics may vary.
What does the test result mean?
The therapeutic range for lithium has been established at 0.6 - 1.2 mmol/L. Within this range, most people will respond to the drug without symptoms of toxicity.
Response and side effects will be individual. For some people with bipolar disorder, their condition will not be adequately treated at the low end of the therapeutic range. Others may experience excessive side effects at the upper end of the therapeutic range. Patients should work closely with their healthcare practitioners to find the dosage and concentration that works best for them.
In general, when lithium results are in the therapeutic range and both the patient and their healthcare practitioner are satisfied that the person's bipolar disorder is being appropriately managed, then the dosage of lithium is adequate, particularly if the person is not experiencing significant side effects.
If the blood level is below the therapeutic range, it is likely that the affected person is not receiving adequate medication. If levels are above the therapeutic range and if there are significant side effects present at the current dose, then it is likely that the dose is too high. In these cases, a healthcare practitioner may adjust the lithium dose. However, patients should not decrease or stop taking their medication without consulting with their healthcare practitioner as it can worsen their bipolar symptoms. Dosage determinations and adjustments must be evaluated on a case-by-case basis.
Is there anything else I should know?
Lithium is eliminated from the body primarily by the kidneys. Long-term use of lithium carries a risk of decreased kidney function.
A variety of prescribed drugs, over-the-counter medications, and supplements can increase, decrease, or interfere with the concentrations of lithium in the blood. For more information, see MedlinePlus Drug Information: Lithium.
Lithium levels and side effects can increase with the loss of salt and water from the body, such as may occur with a salt-free diet, excessive sweating, or with an illness that causes vomiting and diarrhea. To keep blood levels of lithium stable, the National Institutes of Health recommends drinking 8 to 10 glasses of water or other liquids each day, keeping salt and caffeine intake the same as before starting the drug, and avoiding alcohol.
How long will I need to be on lithium?
Who orders lithium tests?
Can I test my lithium level at home?