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The always feeling exhausted comes from being high for long periods of time. If you are not taking some form of insulin I believe that the 436 high number was a bogus meter reading. When you get a number you are not sure about wash you hands and retest at another site. Foreign matter (a sugar soft drink for example) on you skin or hands can blow a meter reading big time. Blood sugar does not normally drop from 436 to 133 in 20 minutes without some insulin help. The false hypo feeling comes from being high for long periods of time as well. A true hypo is usually classified as below 70. The symptoms you mentioned are hypo symptoms and when you feel these coming on test to make sure.
Carbs per day differ for most people due to weight, sex, etc. You can do a google search for this info. I do not think that a low carb diet is healthy, so I try and maintain a medium carb diet of between 80 to 120 carbs per day. I hope this information helps in some way.