In short, your glucose levels are likely too high. Having high blood sugar makes you feel thirsty.
But why does having high blood sugar make you thirsty? That’s a little more complicated.
Type II diabetes happens when your body becomes resistant to insulin, a hormone produced by your pancreas. Insulin acts as a messenger that brings food into your cells. Without insulin, glucose won’t do anything for your cells. When you have Type II Diabetes, your body is still creating insulin, at least initially, but it’s not as effective as it should be.
When your cells can’t take in the glucose, it remains in the blood stream. When glucose is very condensed in the bloodstream, your kidneys lose the ability to draw glucose from water. Normally, nearly all the glucose is pulled out of urine and returned to the body (as is most of the water, depending on your hydration levels). Since your body is no longer able to separate glucose from water in your kidneys, the osmotic pressure builds. Osmotic pressure is the pressure that forms between a liquid with a high solute concentration and a liquid with a lower concentration. The osmotic pressure builds to the point that water can no longer absorb back into your bloodstream, and instead is removed from the bloodstream entirely. Eventually, all the excess glucose will be passed through the urinary tract. However, the sugar cannot remain in the kidneys either, so the kidneys pull water from the rest of the body to remove the sugar. The result is more urination, which in turn causes dehydration as increased amounts of water are eliminated from the body. If you don’t get this problem fixed, the excess water is just going to go through the urinary tract all over again and you will remain dehydrated.