High-sensitivity CRP

Laboratories usually print bands rather than a single range, commonly below 1, 1 to 3, and above 3 mg/L; some print an upper limit of 5. It is the same protein as standard CRP, so any infection or inflammation pushes it far above these bands.

This is the same C-reactive protein as the standard CRP test, but measured with a method that is accurate at very low levels, well below 1 mg/L, where the ordinary test simply reports 'less than 5'. At that fine scale it picks up the low-grade, persistent inflammation that sits in the background in the general population.

Doctors and private services request it, usually alongside a lipid profile, as part of a wider look at heart and circulation health. It is of no use during an infection, when the ordinary CRP does the job.

• Any infection or inflammation, which pushes it far above the low-level bands
• Being overweight, particularly around the waist
• Smoking
• Type 2 diabetes and insulin resistance
• Poor sleep and lack of exercise
• Oestrogen, including some hormone treatments
• Gum disease and other low-grade long-term infections

• Weight loss and regular exercise
• Stopping smoking
• Statins and some other medicines
• Moderate alcohol intake, in the general population

• A cold, a dental infection or a recent vaccination raises it for a few days, so the test is usually repeated two weeks apart when it is high
• Hard exercise in the day before raises it briefly
• It varies from day to day in the same person more than most tests

No fasting needed, but the test is best taken when well, at least two weeks after any infection or injury. Because it varies from day to day, two measurements two weeks apart are often averaged.

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