My grandmother told me that she believes people who aren't diagnosed diabetic shouldn't test their blood sugar more frequently than one day of the week.
I test most days, because I'm an ex-obesity case with numerous mental disorders that either stabilise or go away when my blood sugar stays between 3.3 and 5.0. It started out as just a "because I'm curious" sleep deprived impulse purchase of an Accu-Chek Aviva.
Eating just meat and cheese, I'm normally at the upper end (3.9-5.0) of that range whether fasting or postprandial, and being slightly over (all the way up to 5.9) typically indicates that either I've eaten carbohydrates (at which time such high blood sugars, and higher, would be indicated - I've felt fine up to 6.3, though make no mistake I wouldn't drive a car at that sugar) or that my sleep is dingleberried (usually by being too long, not too short; this usually doesn't take me over 5.5 unless I have also not eaten enough in the past 24 hours, but I have had blood sugars as high as 7.0 (... that was polyuria city!) from extended fasting, and as low as 3.4 from not sleeping).
A major risk with the diet I'm on is scurvy because I don't have a lot of raw food overall. I know when you have a FreeStyle Libre you aren't meant to take ascorbate supplements because it'll throw the results, but my diet is so low in ascorbate (haven't contracted scurvy yet...) that that seems to have thrown Libre's results the other way (yes, I'm wearing a Libre sensor right now, and the site it's at is completely wrong - my left pectoral - so that may be throwing results too). Supplementing by eating a couple strawberries seems to fix the issue without detrimental effects on fingerstick-determined glycaemic control.