Beta cells are responsible for creating and releasing the hormones insulin and amylin, which serve to regulate glucose levels in the blood. Beta cells constitute 65 to 80 percent of the cells in the islets of Langerhans, the endocrine structures in the pancreas. In addition to the hormones they produce, beta cells also release a byproduct of insulin production called C-peptide, which aids in repair of the muscular layers of the arteries, thereby preventing neuropathy and similar complications of vascular deterioration.

Beta cells respond to the body's glucose levels by releasing extra insulin when it is needed. A base level of insulin is maintained in a healthy person's pancreas at all times, but more is released and created in response to a spike in blood glucose, such as that accompanying the digestion of carbohydrates. Beta cells are able to respond rather quickly to a spike in blood glucose, usually in about ten minutes. Amylin, also called islet amyloid polypeptide (IAPP), works in conjunction with insulin by regulating glucose levels in the blood in a more short-term manner.

People who suffer from diabetes have malfunctioning beta cells. In diabetes type I, the body's immune cells destroy beta cells, while in diabetes type II, beta cells gradually stop functioning over time. In both types of diabetes, the lack or reduction of insulin leads to hyperglycemia, or abnormally high blood sugar. Insulin replacement therapy is mandatory for treating diabetes type I and may be required for advanced cases of diabetes type II.

Another malady affecting the beta cells is insulinoma, a rare pancreatic tumor derived from the beta cells which results in unregulated release of insulin, leading to hypoglycemia, or low blood sugar. Medication may be used to regulate this condition, but the only definitive treatment is surgical removal of the tumor. About two percent of people who undergo this surgery develop diabetes type II as a result. In rare cases, a pancreatic tumor releasing excess insulin is cancerous, in which case it is treated with chemotherapy.