What should i do if my blood sugar is 66 and i feel really low with no energy?

Hypoglycemia: Normal blood sugar is 80-100. Have something sweet to eat or drink & consult your physician or endocrinologist.

Nothing: 66 by finger stick is normal. I have never seen a true case of reactive hypoglycemia. The disorder doesn't exist, if you're overweight the symptoms are a natural response to you sugar returning to normal. A glucose tolerance test (if you've had one) is not and never will be a valid diagnostic test for hypoglycemia. Low glucose only ocurrs when treating diabetes, cancer, renal/liver disease.