What is Insulin? - Important hormone allows your body to use sugar (glucose)
What is Insulin?
Written by Amy  Hess-Fischl MS, RD, LDN, BC-ADM, CDE
Insulin is a hormone made by the pancreas that allows your body to use sugar (glucose) from carbohydrates in the food that you eat for energy or to store glucose for future use. Insulin helps keeps your blood sugar level from getting too high ( hyperglycemia ) or too low (hypoglycemia).
The cells in your body need sugar for energy. However, sugar cannot go into most of your cells directly. After you eat food and your blood sugar level rises, cells in your pancreas (known as beta cells) are signaled to release insulin into your bloodstream. Insulin then attaches to and signals cells to absorb sugar from the bloodstream. Insulin is often described as a “key,” which unlocks the cell to allow sugar to enter the cell and be used for energy.
After you eat, cells in your pancreas are signaled to release insulin into the bloodstream.
If you have more sugar in your body than it needs, insulin helps store the sugar in your liver and releases it when your blood sugar level is low or if you need more sugar, such as in between meals or during physical activity. Therefore, insulin helps balance out blood sugar levels and keeps them in a normal range. As blood sugar levels rise, the pancreas secretes more insulin.
If your body does not produce enough insulin or your cells are resistant to the effects of insulin, you may develop hyperglycemia (high blood sugar), which can cause long-term complications if the blood sugar levels stay elevated for long periods of time.
Insulin Treatment for Diabetes
People with type 1 diabetes cannot make insulin because the beta cells in their pancreas are damaged or destroyed. Therefore, these people will need insulin injections to allow their body to process glucose and avoid complications from hyperglycemia.
People with type 2 diabetes do not respond well or are resistant to insulin. They may need insulin shots to help them better process sugar and to prevent long-term complications from this disease. Persons with type 2 diabetes may first be treated with oral medications, along with diet and exercise. Since type 2 diabetes is a progressive condition, the longer someone has it, the more likely they will require insulin to maintain blood sugar levels.
Various types of insulin are used to treat diabetes and include:
Rapid-acting insulin: It starts working approximately 15 minutes after injection and peaks at approximately 1 hour but continues to work for two to four hours. This is usually taken before a meal and in addition to a long-acting insulin.
Short-acting insulin: It starts working approximately 30 minutes after injection and peaks at approximately 2 to 3 hours but will continue to work for three to six hours. It is usually given before a meal and in addition to a long-acting insulin.
Intermediate-acting insulin: It starts working approximately 2 to 4 hours after injection and peaks approximately 4 to 12 hours later and continues to work for 12-18 hours. It is usually taken twice a day and in addition to a rapid- or short-acting insulin. 
Long-acting insulin: It starts working after several hours after injection and works for approximately 24 hours. If necessary, it is often used in combination with rapid- or short-acting insulin.
Insulin can be given by a syringe, injection pen, or an insulin pump that delivers a continuous flow of insulin.
Your doctor will work with you to figure out which type of insulin is best for you depending on whether you have type 1 or type 2 diabetes, your blood sugar levels,and your lifestyle.