People with Type 1 DM produce no insulin. People with Type 2 DM do not always produce enough insulin. Insulin is used medically to treat some forms of diabetes mellitus. Patients with Type 1 DM depend on external insulin (most commonly injected subcutaneously) for their survival because the hormone is no longer produced internally. Patients with Type 2 DM are insulin resistant, have relatively low insulin production, or both; some patients with Type 2 DM may eventually require insulin when other medications fail to control blood glucose levels adequately.