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Lidocaine Hydrochloride Blood Test

Last updated June 11, 2019

Approved by: Krish Tangella MD, MBA, FCAP

The Lidocaine Hydrochloride Blood Test helps determine the levels of lidocaine in blood.

What are other Names for this Test? (Equivalent Terms)

  • Lidocaine HCl Blood Test

What is Lidocaine Hydrochloride Blood Test? (Background Information)

  • Lidocaine is an antiarrhythmic drug used to treat acute ventricular arrhythmia, or disordered heartbeat patterns. Lidocaine works by regulating the flow of electrolytes across heart cell membranes, thus stabilizing the heart rate
  • Specifically, lidocaine makes heart cells harder to electrically stimulate. This increases their electrical stimulation threshold and suppresses their automaticity. This means that lidocaine decreases the ability of the heart muscle cells to cause arrhythmias.
  • The liver breaks down lidocaine within 20 minutes. For this reason, lidocaine is administered continuously through IV, which lengthens its activity to 4 hours
  • 70% of lidocaine breakdown products are bound to proteins in blood. After 2-4 hours of IV administration, 90% of the drug is excreted in the urine as breakdown products (the rest is excreted as intact lidocaine)
  • Like other drugs, lidocaine must be kept within a certain range to prevent unwanted effects. If the levels are too high, it may result in toxicity; if the levels are too low, lidocaine may not help treat heart arrhythmias
  • The Lidocaine Hydrochloride Blood Test helps determine the levels of lidocaine in blood. It is used when adjusting the initial dose, and to ensure that lidocaine levels stay within an acceptable range

What are the Clinical Indications for performing the Lidocaine Hydrochloride Blood Test?

The clinical indications for performing the Lidocaine Hydrochloride Blood Test include monitoring lidocaine therapy.

How is the Specimen Collected for Lidocaine Hydrochloride Blood Test?

Following is the specimen collection process for Lidocaine Hydrochloride Blood Test:

Sample required: Blood

Process of obtaining a blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Lidocaine Hydrochloride Blood Test Result?

A high value (0.6 mg/mL) for the Lidocaine Hydrochloride Blood Test may indicate lidocaine toxicity, which is marked by:

  • Lower back pain
  • Fatigue
  • Nausea, vomiting, diarrhea
  • Altered mental status
  • Abnormal heart rate and abnormal breathing

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Lidocaine is a type of cardiovascular medication. Other types of cardiovascular medications include anticoagulants and antihypertensives
  • Lidocaine is also used as an anesthetic

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

The following DoveMed website link is a useful resource for additional information:


Please visit our Laboratory Procedures Center for more physician-approved health information:


References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 4, 2016
Last updated: June 11, 2019