What usually happens next
Call your doctor today. Diuretics, vomiting and diarrhoea are the usual reasons, and magnesium is checked too, because low magnesium keeps potassium low.
What a low potassium usually means, and its common causes
When a potassium can read wrong
Potassium is the result most often thrown off by the sample. Cells that burst in the tube, a tight tourniquet, clenching your fist, a long wait before the sample is spun, or a very high platelet or white cell count can all make it read high when your blood isn't.
Read it with
Nearby results

Questions
Is a potassium of 2.5 mmol/L normal?
A potassium of 2.5 mmol/L is in the 2.5 to 2.9 mmol/L range usually called moderately low. The usual range is about 3.5 to 5.0 mmol/L (some labs go to 5.1 or 5.3).
Is a potassium of 2.5 mmol/L dangerous?
Between 3.5 and 5.0 mmol/L is the usual range. Just above 5.0 is most often a sample that burst in the tube; 6.0 and over, or under 3.0, is a same-day call to your doctor.
Can bananas raise potassium to 2.5 mmol/L?
Not in people with healthy kidneys, which clear the extra quickly. With reduced kidney function, or on medicines that hold potassium, diet matters more.
Worked out by LifeFrom from the European Resuscitation Council's bands and the usual lab range, and not yet reviewed by a clinician. For your own understanding: only a lab test, read by your clinician, diagnoses anything.