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Lithium Test: What are Normal & Therapeutic Levels?

Written by Mathew Eng, PharmD | Reviewed by Jasmine Foster, BS (Biology), BEd | Last updated:
Jonathan Ritter
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology) | Written by Mathew Eng, PharmD | Reviewed by Jasmine Foster, BS (Biology), BEd | Last updated:

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Lithium Test

Taking lithium is like walking a fine line. A little too much and you may face serious side effects. Not enough and it’s ineffective. For this reason, routine lithium blood level checks are a must. Read on to learn more about the effects of lithium and what levels are considered normal.

What is Lithium?

Lithium is a chemical element that appears as a lightweight, silvery metal [1].

Doctors have long known that lithium is a mood stabilizer. It is one of the oldest drugs for treating bipolar disorder – and is still the preferred treatment to this day [2, 3].

It is also used in other conditions, including depression and certain psychiatric disorders, when first-line drugs don’t work [4].

The human body also naturally carries a small amount of lithium, which we get from food and water [5].

Prescription lithium has a narrow therapeutic window, meaning its blood concentrations need to be within an extremely tight range for it to be effective and safe [2].

Even slightly higher levels can cause side effects. On the other hand, if lithium levels dip too low then bipolar symptoms may reemerge. This is why anyone taking lithium medications requires regular testing [2, 6].

Lithium Blood Test

When It Is Ordered

People who take prescription lithium need to have their levels checked routinely.

Testing is especially important if you’re just starting the medication or if your doctor is changing the dose. Lithium levels are usually checked about 5-7 days after starting a new dose to allow blood levels to stabilize [2, 7].

If you are on a stable dose of lithium, testing intervals can vary, depending on your doctor’s discretion. Monitoring can range from checks every month to checks every 3 months if you’re not experiencing side effects [2, 7].

Your doctor won’t check your levels if you’re not taking lithium medication, unless he or she suspects you’ve been exposed to too much lithium in your environment.

Procedure

Lithium testing requires a blood sample. Ideally, you should undergo a blood draw right before the next scheduled dose, 6-12 hours after your last dose [2].

The results will appear in units of mmol/L (or sometimes mEq/L). This number directly reflects how much lithium is in the blood – also known as a serum or plasma level [2].

Other Tests

Lithium medications often require additional tests and monitoring.

Routine checks of kidney and endocrine (hormone) function are recommended. Doctors may also check electrolytes, calcium, and heart function [2].

Normal Lithium Levels

Therapeutic Level for Bipolar Disorder

If you have bipolar disorder, your doctor will target a very specific lithium blood level. This “normal level” of lithium (better known as the “therapeutic level“) should provide symptom relief while minimizing side effects [2].

Despite its long history of use, there is no universally agreed upon optimal lithium blood level for bipolar treatment. Ranges can slightly vary depending on the country, prescriber, or healthcare organization [2].

For example, the National Institute for Health and Care Excellence in the U.K. recommends a therapeutic level of 0.6 to 1.0 mmol/L for bipolar disorder [8].

On the other hand, the American Psychological Association recommends an initial range of 0.5 to 1.2 mmol/L [9].

One recent study evaluated clinical guidelines from various organizations and countries. They found that the most common therapeutic range is 0.6 to 0.8 mmol/L [2].

What is Normal for Everyone Else?

Besides being a drug, lithium is also an essential micronutrient that the body needs to properly function [10, 5].

However, research about the lithium naturally found in the body (endogenous lithium) is limited. Doctors will rarely check levels in people who aren’t taking lithium as a prescription drug, which makes clinical data almost nonexistent [1].

All in all, this leaves us in the dark as to what a normal range for the general population should be [1].

Despite this, people can be deficient in lithium, which can have negative effects on cognition and behavior [10, 5].

Read our article here to learn more about the effects of lithium deficiency and ways to improve your levels.

Dosage Adjustments

Dosing and target lithium levels need to be adjusted in certain populations.

Younger adults and children often require lower doses to achieve desirable lithium levels [2].

The elderly are much more susceptible to long-term side effects. For this reason, a lower lithium level is targeted in older people [2].

High Lithium Levels

High levels of lithium in the blood can worsen side effects and lead to toxicity [11].

For example, levels above 1.2 mmol/L can cause severe side effects, including nausea, vomiting, and tremors [11].

Very high levels (above 2.0 mmol/L) can cause permanent brain damage and even lead to death [11].

However, side effects can happen even if your levels are normal [2].

The opposite is possible too: your blood levels could be high and you could be free of side effects. How is that possible? Let’s look at how lithium tests work again.

The lab test your doctor orders measures only lithium in the blood, that is, outside your cells and tissues. Lithium needs to enter your cells to have an effect. The test could pick up high blood levels, but your cellular levels could still be normal [12].

More About Lithium

Lithium is usually combined into salts to improve its absorption and distribution throughout the body [13].

In this article, we focused on prescription drugs that typically contain lithium carbonate. They are given at high doses and people who take them require routine monitoring to avoid toxicity. Certain liquid formulations use lithium citrate, which is also available in very low doses over the counter [14].

Lithium orotate, on the other hand, is popular as a supplement. This form of lithium is not approved by the FDA for medical treatment. People take it at much lower doses and don’t need to monitor their lithium blood levels [13].

Lithium orotate might be better at penetrating into the brain, but data about its effectiveness and safety are limited [15, 16, 17, 18].

Check out our lithium orotate article to learn more about the pros and cons of this supplement.

Lithium Diet

Normally, there are no dietary restrictions when taking lithium medications.

However, certain food choices can help keep lithium levels stable. These include [19]:

  • Drinking 8 to 10 glasses of water every day: Dehydration can cause lithium levels in the blood to rise. Drinking a consistent amount of water each day helps to ensure stable levels [19].
  • Keeping your salt and caffeine intake about the same each day: A sudden increase in salt or caffeine intake can reduce lithium levels (and vice versa). The key is to remain consistent [19].
  • Avoiding alcoholic beverages: Alcohol can alter your lithium levels – and it is generally not a good idea in people with mental health conditions [20].
  • Taking lithium with food or milk: this can help reduce stomach-related side effects, like nausea, vomiting, and diarrhea.

Irregular Levels?

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Takeaway

You’ll need to undergo regular lithium blood levels checks if you’re taking prescription lithium. It may seem like a hassle, but these tests are important to make sure the medication is working and the side effects are under control.

The most common therapeutic range for bipolar disorder is 0.6 to 0.8 mmol/L.

However, lithium affects each person differently. Always work with your doctor to find the target level for you.

About the Author

Mathew Eng

Mathew Eng

PharmD
Mathew received his PharmD from the University of Hawaii and an undergraduate degree in Biology from the University of Washington.
Mathew is a licensed pharmacist with clinical experience in oncology, infectious disease, and diabetes management. He has a passion for personalized patient care and believes that education is essential to living a healthy life. His goal is to motivate individuals to find ways to manage their chronic conditions.

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