ESR and CRP are different blood tests used when investigating infection or inflammation. In Sweden ESR is called SR or sänka, while CRP is sometimes called snabbsänka. Neither test alone identifies the location or diagnosis behind your symptoms.
What do they measure?
ESR measures how quickly red blood cells settle in a tube, which is affected by factors including blood protein composition. CRP measures a protein that rises with infection or inflammation. The term snabbsänka does not mean the laboratory is measuring exactly the same thing faster.
The units and reference intervals differ. ESR 30 and CRP 30 should not be treated as the same degree of inflammation. Look at the trend in each individual test and the clinical question being investigated.
A comparison for your results discussion
| Test | What an abnormal result cannot decide |
|---|---|
| ESR, or SR | Does not identify one disease; anaemia and pregnancy can also affect it. |
| CRP | Does not by itself decide whether antibiotics are needed. |
| Both together | Do not replace symptoms, examination and the time course. |
Why can one be high and the other low?
They measure different things, so results can differ. Ask your clinician to interpret the combination in relation to the reason for testing, other blood results and any recent illness. An inconsistent-looking pair of numbers is not itself a reason to order an expanding panel.
Your follow-up checklist
- Which test was taken, in what unit and on which date?
- Was I ill or receiving treatment at the time?
- Is this a new finding or monitoring of an established condition?
- What would another sample help decide and when is it needed?
Contact the clinic that ordered the tests if the plan is unclear. Ask who will review the result and whether follow-up is still needed when you feel better.
Can a low result reassure me despite severe symptoms?
Severe or rapidly worsening symptoms need assessment even if an earlier result was low. Severe breathing difficulty or altered consciousness needs emergency help. Call 1177 in Sweden for advice about new symptoms; an old laboratory number cannot replace a current assessment.
Sources and further reading
Sources and links checked on 22 October 2026. Editorial team: Hagakliniken. General information; individual assessment may differ.