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Does this test have other names?

Lithium levels, serum lithium levels, lithium blood test

What is this test?

This test measures and monitors the amount of lithium in your blood.

Lithium is a medication used to treat psychiatric illnesses such as bipolar disorders, acute mania, and other mood disorders. This test is used to find out the right dose for you if you're just starting lithium treatment and to make sure you continue to get the right amount for as long as you take this medication. 

If you take too much lithium, it can cause more side effects. If you take too little, the drug might not help your condition.

Why do I need this test?

You may have this test once or twice a week when you first start taking lithium to help your doctor figure out the best dose for you.

You may also have this test after you've been taking lithium for a while to see whether your dose needs to be adjusted. You may have this test again five to seven days after your dosage is changed.

You may also have this test if you have symptoms such as tremor, nausea, vomiting, or diarrhea so your doctor knows if your symptoms are because your lithium level is too high or if you have other conditions that need to be treated.  

What other tests might I have along with this test?

Your doctor may also order tests that check how well your kidneys and other organs are working. This is because lithium is excreted through your kidneys; it's not metabolized. These tests may include:

  • Urinalysis

  • Blood urea nitrogen (BUN)

  • Creatinine

  • Calcium

  • Complete blood count

  • Thyroid function

  • Electrocardiogram

Your doctor may also order a pregnancy test, because you shouldn't take lithium during the first three months of pregnancy.

Your doctor may also order other tests while you're taking lithium, to watch how your kidneys and thyroid are working:

  • BUN

  • Creatinine

  • Urinalysis

  • Thyroid function

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Results are given in milliequivalents per liter (mEq/L). For lithium to be effective, your level should be between 0.6 and 1.2 mEq/L, but not more than 1.2 mEq/L.

Lithium has a very narrow range where it is effective and nontoxic. At a level of 1.2 mEq/L, lithium can start to cause problems.

If your levels are too high, you could get lithium poisoning and need treatment immediately. Too much lithium can be fatal. If your levels are too low, the drug may not help your condition.

Levels that are higher or lower may also mean you have cardiovascular or kidney disease.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Timing is important. Having the test 12 hours after your last dose of lithium gives the best results.

Certain medications can affect your results. These include:

  • Antibiotics

  • Arthritis drugs

  • Dilantin, for epilepsy

  • Diuretics, or water pills

  • Nonsteroidal anti-inflammatory drugs, except aspirin

  • Cardiovascular medications, including angiotensin converting enzyme, or ACE, inhibitors and calcium channel blockers

Being dehydrated or a diet too high or low in salt can also affect your results.

How do I get ready for this test?

You don't need to prepare for this test, but note the time you took your last dose of lithium. In addition, be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.