What is the Meaning of Red Flag C Near My Lab Results?


  • Meaning of the letter C beside labs & blood test results
  • When results are flagged with the “C” notation?
  • Why the label “C” printed in the lab test reports?
  • What is the meaning of a Critical Level?
  • Which test results don’t flag with the critical mark “C”?
  • Examples
  • Meaning of reddish double arrows and star

The Abbreviation “C” stands for the word “Critical” which may appear near a lab test result and means that the result is extremely abnormal either high or low. Some labs print that reddish letter “C” beside some of patient’s results to highlight the very risky and urgent lab result, and here some details to read and understand your lab test report easily and effectively.

Also, Critical or Panic values in the laboratory terms mean sudden or prolonged uncontrollable lab test results, often causing another severe complications.

The critical test result is the lab finding that experimented to hold greater health danger or extreme risk by exhibiting mad multiplication of the normal limits.

Generally, the lab finding must be compared to a reference range, a range of two normal limits at least that tell us what’s the normal or abnormal, but sometimes the abnormal values of a lab test exceed the normal limit many times,

for instance, the uric acid test has the normal limits 3 and 6 when the patient’s results found in between these limits it written normal and the patient doesn’t have to receive treatment, if the uric acid result is 6.1 or any value below 11.0 the lab describe it as “high” and have the flag “H” and the patient should receive treatment anytime later to lower uric acid levels but it’s not urgent,

but when the uric acid value jump over the limit 12.0 the lab flag it as “C” which means the uric level is at the critical or panic level because it is double the normal limit and this that must take appropriate treatment promptly without delay.

The reasons of Flag “C” beside the lab test result

The typical reason is that the lab finding is too much high or too much low to the emergency degree that must immediately meet the doctor and take immediate treatment to adjust the blood test to its normal healthy levels, and any delay can prone the patient to great health issues to a very big degree “in ordinary-people words”.

The lab report designated to show the codes like “C” to ensure that the emergency indicators in your results will not miss during exploration of the whole results

Examples of lab tests that may show with “C” mark:

Lab test results that reported in numbers may have critical levels, for instance, the Glucose test, Creatinine test, urea test, Hemoglobin test, HbA1C , Liver enzymes, Testosterone test, COVID-19 antigen and PCR tests, etc.

example show different flags "A""C"
Real-case example of flag “C” on the platelet value

Tests that don’t require the critical mark:

All test that reported in “negative” and “positive” system don’t necessitate to have critical levels, for instance the pregnancy test and qualitative virus B test.

Difference between flag “C” and other flags in the lab report:

Flag “A” means abnormal result but doesn’t distinguish the abnormality if it was low, mild, moderate, or very severe, just mark the result to pay attention to.

Flag “H” means a “High” result obviously but doesn’t distinguish mild elevated from severe elevations, just say the level is outside the higher normal limit.

Flag “C” means not just a high result or just a low result but annotate “extreme elevation or decreasing” in other words the results is “abnormally elevated or decreased many-times over the greater limit of the normal range”

Flag “L” means that the result is “Low” Exclusively but doesn’t provide how low is it.

What to do if your lab results are highlighted with “C” Flag?

Without delay, you must go to the nearest doctor or any healthcare provider to urgently stop the extreme abnormal condition until the results come back normal or near of it.

Other codes in the lab test report

Flag A, Flag L on platelets, Flag H on platelets, and reddish double arrows and star marks, but I will explain that later in another post, so that please follow and save this website to be alert when there is another explanation, also you may send your results to get free interpretation.

Dr.Megan Ralf

A Medical laboratory Scientist who devoted his life to medical and laboratory sciences, writes his everyday expertise dealing with various pathological conditions through laboratory diagnosis of different body fluids, also participating in many workshops for first aids, infection control, and urgent care. Also Dr Megan Ralf coaching many medical teams.

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