Lithium concentration in red blood cells (RBC)
This test measures the amount of lithium, a medication used to manage certain mental health conditions, inside your red blood cells.
["Understanding your lithium RBC levels helps doctors monitor how well your medication is working and whether it’s safe to continue taking it."]
Key facts at a glance
- LOINC
- 25462-3
- Short code
- Lithium RBC-sCnc
- Synonyms
- Lithium RBC-sCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 4.2
- Ref high
- 5.9
- Critical range
- 2 N/A – 7 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85041
- SNOMED
- 900000000000003001
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Doctors may order this test if you’re on lithium therapy to check how your body is absorbing and retaining the medication. It can also help assess long-term exposure, especially if you have kidney issues or take other medications that interact with lithium.
What to Expect Before the Test
No special preparation is needed. A small blood sample is taken from a vein in your arm, similar to other routine blood tests. The sample is then processed to measure lithium levels inside your red blood cells.
What the Results Mean
Lithium levels in red blood cells can differ from those in plasma due to how lithium distributes within your body’s cells. High levels may indicate excessive absorption or impaired elimination, while low levels might suggest insufficient medication or poor adherence.
Common Causes of Abnormal Results
Too much lithium in your system (e.g., from overdose or improper dosing) or kidney problems can raise RBC lithium levels. Conversely, very low levels might occur if your body quickly flushes lithium out or if your medication isn’t working as intended.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Monitoring lithium RBC levels is critical for patients with bipolar disorder or other conditions treated with lithium. Persistently high levels can lead to serious side effects like nausea, tremors, or even kidney damage, while low levels may mean your medication isn’t providing enough protection against mood episodes.
Short name
Lithium RBC Level
Frequently asked questions
Why do doctors specifically test lithium in red blood cells instead of plasma?
What should I do if my lithium RBC test result is outside the expected range?
Can dietary factors (like salt intake) affect lithium RBC levels?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy