or earlier, and porcine lente insulin is also sold and marketed under the brand name vetsulin(sm) in the u.s. for veterinary usage in the treatment of companion animals with diabetes. basal insulin in type 1 diabetes, insulin production is extremely low, and as such the body requires exogenous insulin. some people with type 2 diabetes, particularly those with very high hemoglobin a1c values, may also require a baseline rate of insulin, as their body is desensitized to the level of insulin being produced. basal insulin regulates the body's blood glucose between mealtimes, as well as overnight. this basal rate of insulin action is generally achieved via the use of an intermediate-acting insulin (such as nph) or a long-acting insulin analog. in type 1 diabetics, it may also be achieved via continuous infusion of rapid-acting insulin using an insulin pump. approximately half of a person's daily insulin requirement is administered as a basal insulin, usually administered once per day at night. prandial insulin when a person eats food containing carbohydrates and glucose, insulin helps regulate the body's metabolism of the food. prandial insulin, also called mealtime or bolus insulin, is designed as a bolus dose of insulin prior to a meal to regulate the spike in blood glucose that occurs following a meal. the dose of prandial insulin may be static, or may be calculated by the patient using either their current blood sugar, planned carbohydrate intake, or both. this calculation may also be performed by an insulin pump in patients using a pump. insulin regiments that consist of doses calculated in this manner are considered intensive insulin regimens. prandial insulin is usually administered no more than 15–30 minutes prior to a meal using a rapid-acting insulin or a regular insulin. in some patients, a combination insulin may be used that contains both nph (long acting) insulin and a rapid/regular insulin to provide both a basal insulin and prandial insulin. challenges in treatment there are several challenges involved in the use of insulin as a clinical treatment for diabetes: mode of administration. selecting the 'right' dose and timing. the amount of carbohydrates one unit of insulin handles varies widely between persons and over the day but values between 7 and 20 grams per 1 ie is typical. selecting an appropriate insulin preparation (typically on 'speed of onset and duration of action' grounds). adjusting dosage and timing to fit food intake timing, amounts, and types. adjusting dosage and timing to fit exercise undertaken. adjusting dosage, type, and timing to fit other conditions, for instance the increased stress of illness. variability in absorption into the bloodstream via subcutaneous delivery the dosage is non-physiological in that a subcutaneous bolus dose of insulin alone is administered instead of combination of insulin and c-peptide being released gradually and directly into the portal vein. it is simply a nuisance for people to inject whenever they eat carbohydrate or have a high blood glucose reading. it is dangerous in case of mistake (such as 'too much' insulin). types medical preparations of insulin are never just insulin in water (with nothing else). clinical insulins are mixtures of insulin plus other substances including preservatives. these prevent the protein from spoiling or denaturing too rapidly, delay absorption of the insulin, adjust the ph of the solution to reduce reactions at the injection site, and so on. slight variations of the human insulin molecule are called insulin analogues, (technically "insulin receptor ligands") so named because they are not technically insulin, rather they are analogues which retain the hormone's glucose management functionality. they have absorption and activity characteristics not currently possible with subcutaneously injected insulin proper. they are either absorbed rapidly in an attempt to mimic real beta cell insulin (as with insulin lispro, insulin aspart, and insulin glulisine), or steadily absorbed after injection instead of having a 'peak' followed by a more or less rapid decline in insulin action (as with insulin detemir and insulin glargine), all while retaining insulin's glucose-lowering action in the human body. however, a number of meta-analyses, including those done by the cochrane collaboration in 2005, germany's institute for quality and cost effectiveness in the health care sector released in 2007, and the canadian agency for drugs and technology in health (cadth) also released in 2007 have shown no unequivocal advantages in clinical use of insulin analogues over more conventional insulin types. the commonly used types of insulin are as follows. fast-acting (rapid-acting)