Insulin: What is it and How it Works

The one common factor, in every type of diabetes, is the function of the hormone, insulin. It is responsible for how your body stores and uses the glucose obtained from the carbohydrates you eat. 

The pancreas produces insulin, in what are called beta cells. These cells primary function is to store and release insulin into the bloodstream. The beta cells respond to an increase in the amount of glucose in the blood by secreting insulin. 

Glucose is needed by the body, as it is can easily break it down for energy use. A person with low levels of glucose in their bloodstream may feel lethargic, dizzy, and their muscles may shake. However, a person with high amounts of glucose in their blood may experience blurred vision; a frequent urge to urinate, severe thirst, anxiety, muscle tingling, and fatigue. 

Having an abnormally low or high level of glucose in your bloodstream is dangerous. Having a low amount of glucose may cause your body and brain to shut down; while too much glucose may be toxic. 

A healthy body produces insulin to ensure there is just enough glucose in the bloodstream to function on any given day. The amount a person requires varies according to their daily physical activity. An athlete or a person that exercises regularly may need more glucose. A person who is not as active will need less glucose. 

How Does Insulin Work?  

Understanding how insulin affects your blood sugar level will enable you to understand the different types of Diabetes mellitus. Insulin works to control the glucose in the body in the following way: 

1. When a person eats something, it is digested by their stomach and subsequently passes through the small intestine. Here, it is broken down by enzymes into small sugar units, one of which is glucose. 

• The glucose is absorbed by the blood vessels in the small intestine. It then travels to the cells, or parts of the body that need it; such as the brain or muscle tissue. However, the body does not use all the glucose obtained from food. It also stores some of the glucose in various parts of the body, i.e. the liver, fat and muscle cells. This is especially the case if a person is not physically active; or there is a restriction to their activity in some way, e.g. illness.

• The body releases insulin to control the amount of glucose stored in these cells. This process happens, when blood passes through the pancreas. The pancreas releases the beta cells. If the cells realize there is too much glucose circulating in the body; it will release a proportionate amount of insulin. Insulin then converts the glucose into a form that can be stored. It will not release insulin if the amount of glucose is low.

Without insulin, the human body cannot use glucose or store it for energy. Therefore, glucose will stay in the bloodstream, causing harmful side effects. 

The Negatives of Diabetes  

Although it may feel as though diabetes on its own is bad enough; the effects of being diabetic can carry on beyond just the superficial things you notice at first. Being diabetic means continually trying to balance your blood sugar. When there are too high or too low levels of blood sugar, this affects your whole body.

Cardiovascular Disease

Your heart and blood vessels are especially vulnerable to blood sugar spikes; and this increases your risk of most cardiovascular problems. 

Nerve Damage

High blood sugar can burn or kill the tiny blood vessels that lead to your nerves. Such an action can lead to phantom pain, numbness, digestive problems like nausea or constipation, and even erectile dysfunction. 

Kidney Damage

Because your kidneys do the job of filtering out the excess sugar in your blood; if you have a lot of sugar passing through them, you can damage these delicate organs. Severe destruction may result in kidney failure or end-stage kidney disease; which could require dialysis or a transplant. 

Hand and Foot Damage

As your nerves and blood vessels die, sometimes tissue in your hands; and feet can develop infections and begin to rot. 

Eye Damage  

If the blood vessels and nerves in your eyes are affected; you can experience partial or complete blindness, or develop cataracts or glaucoma. 

Skin Infections

As with hand and foot damage, any cuts to your skin heal poorly and rot, causing infections and sores.

Alzheimer’s Disease

Sometimes called Type-3 Diabetes, Alzheimer’s is much more common in people who have diabetes or poor blood sugar control.

Birth Defects and Stillbirth

Pregnant women who have diabetes have high chances of giving birth to huge babies; babies with low blood sugar or have a stillbirth.

Preeclampsia

Preeclampsia is more common in women with diabetes and can be life-threatening to both mother and baby.

Insulin Types and Quantities

Insulin comes in several different strengths and actions. Long-acting (basal) insulin products such as insulin glargine (Lantus) and detemir (Levemir) are designed to provide up to twenty-four-hour “peakless” coverage. These are frequently prescribed for people with type 2 diabetes starting on insulin therapy. An even longer-acting basal insulin, degludec; is designed to last thirty-six hours, but is not yet approved in the United States (as of mid-2012).

Sometimes mealtime insulin will be recommended for type 2 patients who are having difficulty keeping their postprandial (or after meal) blood sugar levels under control. Rapid-acting insulin such as Humalog, NovoLog; or Apidra is injected before a meal and starts working in fewer than fifteen minutes. Its peak of action (when it is working the hardest) is between thirty to ninety minutes after injection; about the time when blood sugar levels would be at their height after a meal.

Regular Insulin

 Regular insulin starts working thirty to sixty minutes after injection and peaks a bit later than rapid-acting insulin. NPH insulins are longer lasting and have a slower onset and peak action. They are often used in combination with regular insulins. Insulin mixes can also be used to “cover” a meal; and combine longer-lasting NPH insulin with regular acting insulin in different amounts.

It’s important to note that onset, peak; and duration vary from person to person, and can be influenced by other health conditions a person may have, as well as weight. You and your doctor will choose an appropriate insulin; or mix of insulin products based on your particular needs and blood sugar patterns.

The insulin mixes (i.e., 75/25, 70/30, 50/50) are convenient, commonly prescribed insulin combinations. These mixes eliminate your chances of making an error when trying to draw up two different insulin types. They are also a boon to those people who may have vision or dexterity problems; or find mixing insulins difficult for other reasons.

Insulin Dosage

Your insulin dose will depend on the type and action of your insulin. Your doctor will tell you exactly what kind and how much insulin to inject, and when you should be taking it. If you take a long-acting insulin like Lantus or Levemir, you will be injecting once or twice daily.

However, if you take a mealtime insulin, your doctor or diabetes educator will teach you how to determine the amount of regular or rapid-acting insulin you need based on how many carbohydrates you are going to eat. This is called “covering carbohydrates” and you’ll have to do a little bit of math to determine your dose.

Conclusion

This kind of premeal insulin dosing is based on something called the insulin-to-carbohydrate ratio. Everyone has their own unique ratio, but the rule of thumb is that each unit of regular insulin covers about 15 grams of carbs (the insulin-to-carbohydrate ratio). For every 50 mg/dl blood sugar is above the target range, an additional unit of insulin should be added (the blood sugar-to-insulin ratio). So, if you were planning on eating a dinner that has 90 carbs and your blood sugar was 100 mg/dl over target, 8 units of insulin would be necessary (6 to cover the carbs and 2 for the blood sugar). Remember, this is a general guideline only; the insulin-to-carb ratio is different for everyone, as is the insulin-to-blood sugar ratio, and you should work with your diabetes health care provider to track your glucose levels and determine what ratios are right for you.