Plasma Cholinesterase Test; Butyrylcholinesterase

Last updated: February 8, 2026 Medically reviewed by: RxHarun Orthopedic Specialist Doctor Reading time: 5 min read

Plasma cholinesterase; Butyrylcholinesterase; Serum cholinesterase

Serum cholinesterase is a blood test that looks at levels of 2 substances that help the nervous system work properly. They are called acetylcholinesterase and pseudocholinesterase. Your nerves need these substances to send signals.

Serum cholinesterase is a blood test that looks at levels of 2 substances that help the nervous system work properly. They are called acetylcholinesterase and pseudocholinesterase. Your nerves need these substances to send signals. Acetylcholinesterase is found in nerve tissue and red blood cells.

Acetylcholinesterase is found in nerve tissue and red blood cells. Pseudocholinesterase is found primarily in the liver.

In biochemistry, a cholinesterase or choline esterase is a family of esterases that lyses choline-based esters, several of which serve as neurotransmitters. Thus, it is either of two enzymes that catalyze the hydrolysis of these cholinergic neurotransmitters, such as breaking acetylcholine into choline and acetic acid.

How the Test is Performed

A blood sample is needed. Most of the time blood is drawn from a vein located on the inside of the elbow or the back of the hand.

How to Prepare for the Test

No special steps are needed to prepare for this test.

How the Test will Feel

You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.

Why the Test is Performed

Your health care provider may order this test if you may have been exposed to chemicals called organophosphates, which are used in pesticides. This test can help determine your risk of poisoning.

Less often, this test may be done:

To diagnose liver disease
Before you receive anesthesia with succinylcholine, which may be given before certain procedures or treatments, including electroconvulsive therapy (ECT)

Normal Results

Typically, normal pseudocholinesterase values range between 8 to 18 units per milliliter (U/mL) or 8 to 18 kilounits per liter (kU/L).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.

What Abnormal Results Mean

Decreased pseudocholinesterase levels may be due to:

Acute infection
Chronic malnutrition
Heart attack
Liver damage
Metastasis
Obstructive jaundice
Poisoning from organophosphates (chemicals found in some pesticides)
Inflammation that accompanies some diseases

Smaller decreases may be due to:

Pregnancy
Use of birth control pills

FAQ

Why is a cholinesterase test done?

Your health care provider may order this test if you may have been exposed to chemicals called organophosphates. These chemicals are used in pesticides. This test can help determine your risk of poisoning.

What does a low cholinesterase level indicate?

Significantly decreased cholinesterase activity levels usually indicate excessive absorption of organophosphate compounds. Pseudocholinesterase and RBC acetylcholinesterase activity are usually decreased within a few minutes to hours after exposure.

What is the normal cholinesterase level?

Normal Results
Typically, normal pseudocholinesterase values range between 8 and 18 units per milliliter (U/mL) or 8 and 18 kilounits per liter (kU/L). Note: Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your specific test results.

What happens when cholinesterase is high?

If these chemicals get into your body, they can affect how you breathe and can cause general muscle weakness. They are called cholinesterase inhibitors. An overdose of these chemicals can be fatal.

What can cause low cholinesterase?

Reduced cholinesterase levels can also be caused by chronic liver disease and malnutrition. Total cholinesterase activity can be lowered in a number of other conditions, including pregnancy, renal disease, shock, and some cancers.

How is low cholinesterase treated?

There is no cure for pseudocholinesterase deficiency. If you have the condition and you receive muscle relaxants that prolong your anesthesia recovery, you’ll likely need medical assistance. If needed, mechanical ventilation support and sedation are provided while you recover and start breathing on your own.

What causes high cholinesterase?

Several conditions are associated with increases in plasma cholinesterase activity, including thyroid disease, obesity, nephrotic syndrome, and cognitively challenged children.

When should a blood test for baseline cholinesterase be done?

When obtaining the 2nd baseline, wait to test until at least 3 days after the baseline, but within 30 days, and ensure no pesticide exposures during this time period. Measure both acetylcholinesterase (red blood cell cholinesterase-AChE) and butyrylcholinesterase (plasma cholinesterase-PC).

How is cholinesterase measured?

How is a cholinesterase test performed? Cholinesterase is a blood test and requires a few milliliters of blood from a vein. The laboratory may measure the levels of cholinesterase enzyme activity in the plasma or red blood cells or both.

Where is cholinesterase produced?

In the liver
Cholinesterase is a plasma enzyme, produced by the liver, which is capable of hydrolyzing a variety of choline esters. Plasma activity falls with decreased protein synthesis in liver disease. Enzyme levels generally follow a path similar to that of plasma albumin.

What are the side effects of cholinesterase inhibitors?

The most common adverse effects of cholinesterase inhibitors include nausea, diarrhea, vomiting, decreased appetite, dyspepsia, anorexia, muscle cramps, fatigue, insomnia, dizziness, headache, and asthenia. 1–3 Taking these medications with food, preferably a full meal, can mitigate these gastrointestinal effects.

Is cholinesterase affected by pH?

With most substrates, the enzyme activity increased from pH 5 to pH 10 and decreased at pH 11. Acetylcholine and acetyl-β-methacholine showed an activity maximum at pH 7 or 8. Inhibition by the selective inhibitor of specific cholinesterase 284 C 51 was not markedly affected by pH.

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

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Written by Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist

Dr. Md. Harun Ar Rashid, MPH, MD, PhD, is a highly respected medical specialist celebrated for his exceptional clinical expertise and unwavering commitment to patient care. With advanced qualifications including MPH, MD, and PhD, he integrates cutting-edge research with a compassionate approach to medicine, ensuring that every patient receives personalized and effective treatment. His extensive training and hands-on experience enable him to diagnose complex conditions accurately and develop innovative treatment strategies tailored to individual needs. In addition to his clinical practice, Dr. Harun Ar Rashid is dedicated to medical education and research, writing and inventory creative thinking, innovative idea, critical care managementing make in his community to outreach, often participating in initiatives that promote health awareness and advance medical knowledge. His career is a testament to the high standards represented by his credentials, and he continues to contribute significantly to his field, driving improvements in both patient outcomes and healthcare practices. Born and educated in Bangladesh, Dr. Rashid earned his BPT from the University of Dhaka before pursuing postgraduate training internationally. He completed his MD in Internal Medicine at King’s College London, where he developed a special interest in inflammatory arthritis and metabolic bone disease. He then undertook a PhD in Orthopedic Science at the University of Oxford, conducting pioneering research on cytokine signaling pathways in rheumatoid arthritis. Following his doctoral studies, Dr. Rashid returned to clinical work with a fellowship in interventional pain management at the Rx University School of Medicine, refining his skills in image-guided joint injections and minimally invasive pain-relief techniques.