Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Dehydration is a condition that can occur when the loss of body fluids, mostly water, exceeds the amount that is taken in. With dehydration, more water is moving out of individual cells and then out of the body than the amount of water that is taken in through drinking. The problem is that along with the water, small amounts of salts or electrolytes are also lost for this reason the body also needs replacement of electrolytes (for example, potassium and sodium) to complete back the balance of water and electrolytes the body has lost. Heat exposure is a common cause of dehydration and weakness or tiredness are important symptoms that may suggest this condition. Other symptoms and signs can be dry mouth,increased thirst and orthostatc hypotension. Here are my advices for you: - Drink plenty of water , -Drink carbohydrate/electrolyte-containing drinks like sports drinks that replace lost nutrients -Cool the body -Remove any excess clothing. This will help you to stabilize the water and electrolyte equilibrium. About the sugar and carb intake, I can say that this can probably cause reactive hypoglicemia and in these circumstances you may fell weakness but this symptom disappear soon and it is not persistent. This condition is also known as postprandial hypoglycemia and consist in drops in blood sugar that are recurrent and occur within four hours after eating. In my opinion this is not the cause of your sudden and persistent symptoms. Anyway i suggest to consult physically your physician because it is necessary to do some blood tests(to see if you have electrolyte imbalance or a possible anemia)to reach the right diagnosis. Only than you can have the right treatment. Hope I have answered your query. Let me know if I can assist you further.