Why does canesten oral say not to use it if you have a potassium, magnesium, or calcium deficiency? is it not safe? if i have any of these deficiencies is it still safe to take it locally as a cream? i would prefer to take it orally if it is safe to?

I think Fluconazole is the main ingredient of Canesten in Australia and it can be used orally. People with K, Mg or Ca deficiency are at risk for prolonged QT / cardiac arrhythmia and Fluconazole potentiates this risk. If you are healthy, Fluconazole can be taken by mouth if indicated. In outpatient setting most of the time Fluconazole is prescribed without a blood test for electrolytes.