My insulin levels came back at 72. I was told this was 3 times the highest of normal reference range. What does this mean and is it serious?

Insulin resistance s. Yes, serious, need to lose weight. If you are not diabetic, you're about to become one as your pancreas cannot keep up with the demands with your diet. Lose the carbs and give your pancreas a break.
LIKELY PRE-Diabetes. Yes, normal fasting Insulin level=5-20. High insulin, even with normal blood sugar, may indicate that the pancreas is working harder than normal to lower the blood-sugar level. This is "insulin resistance syndrome." this is seen in overweight people with pcos & pre-diabetes. Another important reason for measuring the blood Insulin level is to diagnose or evaluate low blood sugar (hypoglycemia).