To measure lithium levels in the blood in order to determine the therapeutic level when just starting lithium medication; to monitor levels to ensure they are maintained in the therapeutic range; and sometimes 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) levels
A blood sample drawn from a vein
No test preparation is needed. However, timing of the sample collection may affect results. Generally, lithium blood levels are measured 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 approved by the U.S. Food and Drug Administration (FDA) as an antipsychotic for the treatment of bipolar disorder. Occasionally, it can be used in other disorders in combination with an antidepressant that does not adequately treat a depression. This test measures the amount of lithium in the blood.
Bipolar disorder can affect both adults and children. It is a mental condition marked 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 an episode of depression, you may feel sad, hopeless, worthless, and lose interest in daily activities. You may be fatigued but have trouble sleeping, experience weight loss or gain, have difficulty concentrating, and have thoughts of suicide.
- During a manic episode, you may be euphoric, irritable, have high energy and grandiose ideas, use poor judgment, and participate in risky behaviors. Sometimes you will have mixed episodes with aspects of both mania and depression.
Lithium is prescribed to stabilize the mood swings of 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 disorders with symptoms of schizophrenia (e.g., hallucinations, delusions) 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 up or down until blood levels are within a therapeutic range—the blood level range that achieves the desired effect and treats your 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 your age, general state of health, and other medications that you are taking.
Lithium levels are monitored on a regular basis because lithium has a narrow therapeutic index. This means there is relatively little space between therapeutic and toxic levels. Too little drug, and the medication will not be effective. Too much drug and symptoms of lithium toxicity may develop.
How is the test used?
The lithium test is used to measure and monitor the amount of lithium in your blood so that a healthcare practitioner can determine whether the drug blood level is within the range that will adequately treat your bipolar disorder (therapeutic range). The test may be used to measure blood levels every few days when you first begin 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 levels. If you start taking additional medications, your healthcare practitioner may order one or more lithium tests to judge the other drugs' effect, if any, on lithium levels. Lithium tests may also be ordered if toxicity is suspected.
When is it ordered?
Lithium testing is ordered frequently when you first start lithium treatment. After you have achieved stable blood levels in the therapeutic range, your healthcare practitioner may order lithium tests at regular intervals to ensure that drug levels remain in this range.
The test may be ordered when your condition does not appear to be responding to lithium to determine whether levels are too low, the medication is not working, and/or to determine if you are complying with therapy (taking the lithium regularly). It may also be ordered when you experience a troublesome level of side effects and/or exhibits symptoms that your healthcare practitioner suspects may be due to toxicity, such as:
- Symptoms of an allergic reaction to lithium, such as hives, difficulty breathing, swelling of the face, lips, tongue, or throat
- Drowsiness, lack of energy
- Muscle weakness
- Lack of coordination
- Slurred speech
- Gastrointestinal side effects such as nausea, vomiting and/or diarrhea
- Irregular tremors or shaking
- Urinating frequently
- Feeling very thirsty
Extremely high levels can lead to stupor, seizures, kidney 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 vary among individuals. 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. You should work closely with your healthcare practitioner to find the dose that works best for you.
In general, when lithium results are in the therapeutic range and both your and your healthcare practitioner are satisfied that your bipolar disorder is being appropriately managed, then the dosage of lithium is adequate, particularly if you are not experiencing significant side effects.
If the blood level is below the therapeutic range, it is likely that you are 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, your healthcare practitioner may adjust the lithium dose. However, you should not decrease or stop taking your medication without consulting with your healthcare practitioner as it can worsen your bipolar symptoms. Dose determinations and adjustments must be evaluated on a case-by-case basis.
How long will I need to be on lithium?
Who orders lithium tests?
Can I test my lithium level at home?
What other lab tests might be ordered after I begin taking lithium?
Other blood and urine test may be needed to check for unwanted side effects. Lithium has adverse effects on the kidneys, thyroid gland and parathyroid glands, which requires a close monitoring of the proper functioning of these organs through periodic blood tests:
- Lithium is eliminated from the body primarily by the kidneys. Long-term use of lithium carries a risk of decreased kidney function. People with kidney disease and reduced kidney function may have increased lithium levels because it takes the kidneys longer to clear the drug from the body. Healthcare practitioners will monitor kidney function over time with tests such as BUN and serum creatinine.
- People who take lithium may develop underactive thyroid (hypothyroidism). Healthcare practitioners will often regularly monitor your thyroid function both before and during lithium treatment with a thyroid stimulating hormone (TSH) test. Other tests such as T3 and T4 are also recommended.
Is there anything else I should know?
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.