You have what is known as orthostatic hypotension
because of autonomic neuropathy which is not uncommon with diabetes
. There are certain drugs which can help you with this (this can be prescribed by your doctor). You can start off by taking some multivitamins & Conenzyme Q10 (a health supplement) on your own. When you do get up dont try to get up suddenly , take a little time for switching from sitting to standing up position.
Hope I have answered your query. If you have any further questions I will be happy to help
Dr. Om Lakhani