Insulin is a natural protein made by the pancreas that helps the body use sugar. Insulin is injected by all people with type 1 (insulin-dependent) diabetes mellitus and by some people with type 2 (non-insulin-dependent) diabetes mellitus to help control blood sugar levels.

Any substance (dietary, supplemental, herbal, and others) that affects blood sugar levels will directly or indirectly affect the amount of insulin required by a person with diabetes. For example, consumption of a high-fiber diet and/or supplementation with nutrients such as chromium, biotin, vitamin E, or herbs such as Gymnema sylvestre will often improve blood sugar control in diabetics. In such cases, the amount of insulin may need to be reduced in order to avoid a hypoglycemic reaction. Anyone taking insulin should consult the prescribing physician before making dietary changes or taking nutrients or herbs that are designed to lower blood sugar levels.