When i stand up, my blood pressure decreases but my heart rate increases. is this normal?

Dehydration: If you are dehydrated, the volume of blood in your blood vessels is decreased. Therefore when you stand up there is not enough blood to sustain your blood pressure. The heart tries to compensate for the low blood volume by beating faster. If you are continuing to have diarrhea, you must increase your fluid intake and mineral/electrolyte by drinking a sports typpe drink.