13. Nerve Damage
As blood sugar builds up, this can interfere with the circulation of blood around the body. This then leads to nerve damage which can reveal itself in a number of ways. Nerve damage can cause dull pain in the lower extremities (feet and legs) and it can cause coldness and numbness. It may also lead to headaches, blurry vision, and to slow healing of wounds.
All of these things are signs that diabetes has progressed and they can all be very dangerous if they are allowed to progress: leading to the loss of limbs or permanent eyesight damage in some cases. If you notice these symptoms then you need to see a doctor immediately for a course of insulin. Of course, the preferable alternative is that you notice the other symptoms sooner and avert this situation altogether!