The lithium test is used to measure and monitor the amount of lithium in the blood so health care providers can determine whether drug concentrations are in the 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 health care provider 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.
Lithium is ordered frequently when a person is starting lithium treatment. After a person has stable blood concentrations in the therapeutic range, a health care provider may order monitoring 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 doctor suspects may be due to toxicity such as:
Drowsiness, lack of energy
Lack of coordination
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.
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 health care providers 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 health care provider 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. However, patients should not decrease or stop taking their medication without consulting with their health care provider as it can worsen their bipolar symptoms. Dosage determinations and adjustments must be evaluated on a case-by-case basis.
Lithium is excreted primarily by the kidneys. Long-term use of lithium carries a risk of decreased kidney function. People with kidney disease may have increased lithium levels because of decreased elimination. Doctors will monitor kidney function over time with tests such as BUN and creatinine.
Patients who take lithium may develop hypothyroidism. Doctors will often regularly monitor a person's thyroid function with a TSH test.
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 (NIH) 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.
This article was last reviewed on July 23, 2013. | This article was last modified on May 29, 2015.
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