Cholinesterase: what it is, what it tells you and when it’s tested

Serum cholinesterase is an enzyme made by the liver that circulates in your blood. Its exact job is not fully understood, but it breaks down some medicines and some toxic substances. The value mainly shows how well your liver makes its proteins.

When it’s tested

Doctors order it in three cases. To see how the liver is working, mostly in people with a known liver condition. Before an anaesthetic, if you or a relative woke up very slowly after an operation. And in people who work with pesticides, or think they have been exposed to them.

It is not a useful test for people who feel well. The value varies a lot from person to person and from lab to lab, and on its own it says little. That is why Rosa does not test it. Instead it measures albumin, ALT and AST, gamma GT and bilirubin, which show how your liver is doing.

What it tells you, and what it does not

If it is low, your liver may be making fewer proteins, as happens in advanced liver disease or malnutrition. It also falls with a serious infection or inflammation.

A low value can also come from a genetic variant that is harmless in everyday life and only matters under anaesthesia. Or from contact with some pesticides.

It does not say which of these causes applies. Your history, an examination and other tests answer that.

That is why it is read together with other tests:

Normal cholinesterase levels

Here, more than for most tests, the lab decides what is normal. Different methods give very different numbers: the same blood can be normal at one lab and out of range at another. Some reports use U/L, others kU/L.

That is why only the range printed on your report counts. If you need to repeat the test, it is best done at the same lab.

In young women, in pregnancy and on the pill the value is usually a little lower, and many labs print different limits for them.

If your cholinesterase is low or high

What can lower it

The most common causes of low cholinesterase:

Cholinesterase and anaesthesia

During an operation, doctors sometimes use medicines that relax the muscles for a few minutes. Cholinesterase is what breaks them down.

People with a genetic variant, or a very low cholinesterase, clear them slowly: after the anaesthetic they can stay paralysed and on a breathing tube for longer than expected. In the operating theatre doctors handle this, but it is better to know beforehand.

If this has happened to you or a relative, tell the anaesthetist before any operation. They can order this test and choose other medicines.

When to worry

Watch for these cases:

Frequently asked questions

What are normal cholinesterase levels? It depends a lot on the lab’s method, so there is no single number that works for everyone. The range on your report counts, and it may differ for women and men.

Low cholinesterase: what does it mean? Often that your liver is making fewer proteins, or that there is malnutrition or an infection. It can also come from a genetic variant or pesticides. Your doctor reads it together with your other liver tests.

High cholinesterase: is it a problem? Usually not. It is seen more often in people with excess weight, diabetes or a fatty liver. That is why your doctor looks at blood sugar, triglycerides and the liver instead.

Why is cholinesterase tested before an anaesthetic? Because it breaks down some muscle-relaxing medicines. If it is very low, their effect lasts longer. It is mostly ordered when similar problems have happened in the family.

Is cholinesterase checked in people who work with pesticides? Yes, occupational doctors sometimes use it to see whether there has been exposure. A low value points to exposure, but it does not say how serious it is, and a normal value does not fully rule it out. If you feel unwell after contact, call 112 or go to the emergency department.

Does Rosa test cholinesterase? No. Rosa measures albumin, ALT and AST, gamma GT and bilirubin, which show how your liver is doing. If your doctor wants cholinesterase, they order it separately.

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