What causes numbness in the feet when blood sugar is high?

High blood glucose levels accompanied by numbness in the feet may result from diabetic peripheral neuropathy, cerebrovascular disease, or cervical or lumbar spine disorders.

1. Diabetic Peripheral Neuropathy

Prolonged poor glycemic control in patients with hyperglycemia commonly leads to diabetic peripheral neuropathy, which damages peripheral blood vessels and nerves, resulting in foot numbness.

2. Cerebrovascular Disease

In patients with hyperglycemia who also have cerebrovascular disease—such as stroke or cerebral hypoperfusion—the sensory nerves may be adversely affected, leading to nerve damage and subsequent foot numbness.

3. Cervical and Lumbar Spine Disorders

In patients with hyperglycemia who concurrently suffer from cervical or lumbar spine disorders, posterior disc herniation may compress central nervous structures, causing weakness and numbness in the limbs—including the feet. In lumbar spine disease, excessive physical strain on the lower back or prolonged improper sitting posture may lead to nucleus pulposus herniation, compressing local nerves and resulting in symptoms such as leg pain and foot numbness.