Very often words “diabetes” and “insulin” are used together in conversation. That is to underline the strong relationship between human hormone insulin and the disorder of many called diabetes. Very often insulin is perceived as the only treatment of diabetes. However, that is not absolutely true, at least for those who suffer from type 2 diabetes. The rest 10 % of all diabetes cases refer to type 1 diabetes, and for them insulin is the primary treatment option and the only way to keep the disorder under control.

Insulin is human hormone, which derived its name from the Latin word “insula”, which means “island”. It was obviously called so because this hormone is produced in certain areas of human pancreas, known as islets of Langerhans.

The major role of insulin is to supply all the cells of human body with glucose. Glucose or blood sugar, derived from foods rich in carbohydrates, is the major source of energy and a kind of fuel, required for maintaining all the major processes in the cells, such as growth, movement, replication and others. But glucose cannot penetrate into the cells without insulin – here the hormone works like a key, which “opens” the cells’ membranes, letting fuel in.

That is why once we eat some carbohydrates-containing food and it is broken down by stomach acid into a range of simple compounds, including glucose, - human pancreas releases insulin in the particular amount, necessary for delivering glucose into the cells of human body.    

What happens when the body stops producing insulin?

In case of type 1 diabetes, human pancreas does not produce insulin at all. As the result, all the sugar (glucose) remains in the blood instead of penetrating the body cells and supplying calories of energy to them. Remained unused glucose is then moved out from the body with urine.

As the result of insulin deficiency, all the cells throughout the human body are deprived of the opportunity to get energy from glucose, and from the consumed foods, on the long run. Energy source is still present in the bloodstream, but it is beyond the reach of cells without insulin.

It is needless to say that without glucose, as the major source of energy, malfunctions occur in all the body systems and processes. That is why people with type 1 diabetes should receive insulin from the external sources.

All the cases of type 1 diabetes, when insulin is no longer produced in the body, are managed by regular injections of exogenous insulin. Unfortunately, insulin is very “delicate” substance and gastric acids of the digestive tract can easily destroy it – that is the reason why insulin should be delivered subcutaneously by injection, and not by simple pills, taken by mouth.

Initially, the sources of insulin for treating diabetes in people were some animals, like cows and pigs. In the past decades the manufacturers succeeded greatly at purifying such insulin (earlier contaminations, causing certain allergic reactions in people, have been the major concerns among doctors and patients). However, in spite of the great progress in the technology of producing and purifying insulin from animal sources, nowadays there is no beef or pork insulin available on the U.S. market.

Synthetic human insulin, produced using the DNA recombinant technique, is the only available insulin for diabetes treatment these days. Scientists learned to insert a part of human DNA into a host cell of certain types of bacteria or yeast. In that way those microorganisms are turned into small factories of synthetic insulin, which they produce in the process of their vital activity. Such hormone, appearing thanks to a combination of highly-sophisticated genetic engineering techniques and the simplest living organisms, is considered to be the best substitute of natural human hormone.

What are the types of insulin available on the market?  

Insulin products, manufactured and marketed today, are categorized based on the certain features: onset of action (how quickly insulin starts working), peak time (the time when insulin is the most effective), and duration of action (how long it stays effective in the body). This allow doctors to choose the best product or combination of products to suit the diabetes profile of an individual, taking into account his personal response to insulin, eating and exercising habits, and a number of other factors.

Below is the table summarizing the key characteristics of the available insulin products (based on the data provided by the FDA).

Type of Insulin	Examples	Onset of action	Peak action	Duration of action
Rapid-acting	Humalog	15 minutes	30-90 minutes	3-5 hours
	NovoLog	15 minutes	40-50 minutes	3-5 hours
Short-acting (Regular)	Humulin R Novolin R	30-60 minutes	50-120 minutes	5-8 hours
Intermediate-acting (NPH)	Humulin N Novolin N	1-3 hours	8 hours	20 hours
	Humulin L Novolin L	1-2.5 hours	7-15 hours	18-24 hours
Intermediate- and short-acting mixtures	Humulin 50/50 Humulin 70/30 Humalog Mix 75/25 Humalog Mix 50/50 Novolin 70/30 Novolog Mix 70/30	The onset, peak, and duration of action of these mixtures would reflect a composite of the intermediate and short- or rapid-acting components, with one peak of action.
Long-acting	Ultralente	4-8 hours	8-12 hours	36 hours
	Lantus	1 hour	none	24 hours

Insulin therapy is a very complicated process and it should not be simplified just to choosing a particular product. Right timing, type and insulin amount are the key components of successful diabetes management.