Monocytes

Some laboratories use 0.2 to 0.8; use the range your lab printed.

Monocytes are white blood cells that move from the blood into the tissues, where they become macrophages, the cells that clear up debris, engulf microbes and help to set off longer-term immune responses. This is the absolute number in a given volume of blood.

It is part of the full blood count differential. Doctors note it during long-standing infections and inflammatory illnesses, and a persistently high count is one of the things that prompts a look at the bone marrow.

• Long-standing infections such as tuberculosis and endocarditis
• Recovery from an infection or from chemotherapy
• Long-term inflammatory conditions, including inflammatory bowel disease
• Smoking
• Some blood and bone marrow conditions
• Steroid medicines, in some people

• Chemotherapy and other bone marrow suppressing medicines
• Severe infection
• Some bone marrow conditions
• Hairy cell leukaemia, a rare blood condition

• A rise while recovering from an infection is expected
• Smokers sit a little higher in the general population
• Analysers count monocytes with less precision than neutrophils, so small day-to-day differences are common

No fasting needed. A single high count is usually repeated after a few weeks before any further tests.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.