Serum Blood Levels and Medication

Nurse taking blood from patient in hospital
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Serum blood level describes the amount of a given medication present in your blood at the time of testing. Many medications used to treat bipolar disorder have what is known as a small "therapeutic window" meaning the difference between a therapeutic level and toxic level can be small in some individuals. The only way to test these levels for a certain medication is to test a person's serum blood levels. By doing so, that window can be assessed and the proper dosage for a certain medication can be given.

What Is Serum Blood Level?

Blood serum is the liquid part of the blood that contains no clotting factors or blood cells. When doctors check for serum blood levels, they are usually checking for lithium levels in the bloodstream to be sure that the right dosage is being administered. If other medications are being taken, blood serum levels could be monitored regularly to ensure that lithium is not interfering with the medication. Specifically, 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.

Some patients may be more or less sensitive to lithium and thus need to be tracked to alleviate side effects and avoid toxicity of medication.

Medications That Require Testing

In addition to lithium, some medications used to treat bipolar disorder require serum blood level testing. Other medications that require serum blood level testing include Tegretol (carbamazepine) and Depakote/Depakene (sodium valproate, valproic acid) as well as certain tricyclic antidepressants such as Pamelor (nortriptyline) and Anafranil (clomipramine).

Testing serum blood levels are usually done before medication is prescribed and follow-up can be as soon as one week up to every 6 months or more, depending on your physician's treatment strategy and how the medication is affecting your bipolar disorder. The test is usually performed by a professional phlebotomist in a lab or clinic setting. The blood is then separated into serum using a centrifuge. This separates the serum to be tested.

Serum Blood Levels and Your Kidneys

Long-term lithium treatment can result in chronic kidney disease. For this reason, serum blood levels may be monitored to check kidney function while the medication is being given for bipolar disorder. For kidney function in lithium treatment, a 24-hour urine collection may also be done to measures total volume output, creatinine levels, and creatinine clearance, and compares it to the norm based on weight and height (total square footage of surface area).

Other medications used for bipolar disorder may also cause kidney issues depending on how long and how frequently the drugs are used. A total serum protein test may be conducted to check organ function. Specifically, globulin and albumin levels will be checked.

High globulin or low albumin levels are causes for concern.

Other Important Serum Blood Tests

Your doctor may test your serum blood levels for sodium, magnesium, cholesterol and other important levels that may indicate changes in your blood profile. Serum blood levels showing increased levels of these markers may spell an increased risk for chronic medical conditions or psychotic episodes. Talk to your doctor if you feel serum blood level testing may help you assess your health.

5 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Mannapperuma U, Galappatthy P, Jayakody RL, Mendis J, De silva VA, Hanwella R. Safety monitoring of treatment in bipolar disorder in a tertiary care setting in Sri Lanka and recommendations for improved monitoring in resource limited settings. BMC Psychiatry. 2019;19(1):194. doi:10.1186/s12888-019-2183-7

  2. Rej S, Herrmann N, Gruneir A, et al. Blood Lithium Monitoring Practices in a Population-Based Sample of Older Adults. J Clin Psychiatry. 2018;79(6). doi:10.4088/JCP.17m12095

  3. American Association for Clinical Chemistry. Lithium.

  4. American Association of Clinical Chemistry. Carbamazepine.

  5. National Kidney Foundation. Lithium and Chronic Kidney Disease.

By Marcia Purse
Marcia Purse is a mental health writer and bipolar disorder advocate who brings strong research skills and personal experiences to her writing.