I'm 74 & have taken metf (3x500 mg) for about 10 years, with no problems, either perceived or blood test.
Low BG hypos are not likely with metf, & treatment with metf does not affect car insurance or problems with the DVLA.
I am on a low carb, high fat diet & play tennis for 2-3 hours without sports drinks or bananas. A low carb, even Atkins diet should not cause problems due to low BG.
In diabetics, BG changes continuously through the day, being at the maximum about 1 hour after a meal, & a minimum before the next meal. A single figure doesn't tell us much - unless that 71.8 was measured when you felt low. It isn't low - it is still well above the non-diabetic level & well above the hypo level. If that was your BG when you felt ill, there is some other cause likely & you should watch for other symptoms. Are you taking other medication? e.g. Statins are much more likely to cause problems than metf.