Most people have hypoglycemic feelings when under 3.9 mmol/L ( 70 mg/dl ). A diabetic must be concerned about low glucose levels because a diabetic often injects insulin or takes medication to lower their blood glucose and as the cannot reduce a dose after it has been injected or swallowed, lowering glucose levels can be very dangerous hence the jelly bean advice from your friend cause a diabetic must correct the situation manually. A non-diabetic who wouldn't be on insulin or medications for diabetes has little to fear from such symptoms but a quick snack should resolve the symptoms promptly.
Normally, a glucose test would be done fasting and done two hours after a meal ( postprandial ). The postprandial is considered normal if it's under 7.8 mmol/L ( 140 mg/dl ) and diabetic when it's 11.1 mmol/L ( 200 mg/dl ) or higher. As it's doubtful that you took a reading at a useful time, you should see your Doctor and get a HbA1c test done.
As your measurement of 3.7 mmol/L was 30 minutes after your meal, you must've had a very high glycemic meal. The insulin your body produces lasts longer than very sugary food. You should divide your meals down into smaller, more frequent meals, select lower glycemic index alternatives and even replace or omit some cards. However 8.9 mmol/L is a little high, you may be prediabetic.
