Insulin is a hormone that plays an important role in the body's metabolism by controlling blood sugar levels and other processes.
It is produced by beta cells in the pancreas and released it into the bloodstream after we eat to enable some body cells, such as muscle, fat, and heart cells, to absorb the sugar from the food we eat.
Insulin also helps store glucose in the liver as glycogen when it is not needed, so it can be released when blood sugar levels are low or when more energy is needed.
Therefore, insulin is essential for regulating blood sugar, ensuring that levels remain within certain limits and do not climb too high or fall too low.
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What is insulin sensitivity factor?
Insulin sensitivity factor, or correction factor, refers to the number of milligrams per deciliter (mg/dl) fall in blood sugar levels caused by taking 1 unit of insulin.
Insulin sensitivity factor reflects how blood sugar levels fall after taking 1 unit of insulin.
Knowing this number can help people with type 1 diabetes lower their blood sugar levels when they are out of their target range. This is usually added to the premeal insulin dose and is based on how much higher the person's blood sugar level is compared to their target.
Target blood sugar levels need to be determined in discussions with a doctor. According to the American Diabetes Association, they should be as close as possible to healthy non-diabetic levels of:
- Between 70 and 130 mg/dl before a meal
- No higher than 180 mg/dl up to 2 hours after a meal
Insulin treatment plans vary, but most people with type 1 diabetes are now on a basal-bolus insulin routine. A basal-bolus insulin routine involves injecting a longer-acting form of insulin to keep blood sugar levels stable between meals and when sleeping and injections of faster-acting insulin to cover meals.
For people on a pump, an amount of fast-acting insulin is delivered throughout the day and night by the pump, with another amount of insulin delivered for mealtimes.
Among people on this routine, the "1,800 rule" is often used to determine the amount of rapid-acting insulin needed to drop blood sugar a certain amount. This works by dividing the number 1,800 by the total average daily dose of fast-acting insulin.
For regular insulin, 1,500 would be used instead of 1,800, though few people use this type of insulin anymore.
For example, let's assume a person is taking a total of 30 units of rapid acting insulin through the day
Dividing 1,800 by 30 would give an insulin sensitivity factor of 60. This means that 1 unit of fast-acting insulin would reduce this person's blood sugar levels by 60 mg/dl.
If their target goal was to have their glucose at 100 mg/dL before meals, but their glucose was actual 220 before the meal, the person would add 2 units of fast-acting insulin (220-100=120; 120/60=2) to their insulin amount for that meal.
When to test for insulin sensitivity factor
Insulin sensitivity factor can be affected by many things during the course of the day. As a result, choosing the right time to test is important.
Doctors recommend that insulin sensitivity factor should only be assessed when:
- Blood sugar levels are at least 50 mg/dl above target
- No food has been eaten for at least 4 hours
- No food will be eaten for the next 4 hours
- A bolus insulin dose has not been taken for at least 4 hours
Times to avoid testing for insulin sensitivity factor include:
- After strong physical activity
- During the course of an illness or infection
- After a period of low blood sugar levels
- During emotional stress
To test their insulin sensitivity factor, an individual should first check and record their blood sugar levels and take a correction dose of insulin based on their current sensitivity factor. They should then retest your blood sugar levels 2 and 3 hours after taking the insulin dose.
If their ratio is correct, their blood sugar level should be within a 40 point range of their target. If it is out of this range on two or more occasions, they may need a change in their correction factor. Further testing may be required to confirm the results.
If blood sugar levels drop below 70 mg/dl during the testing period, the assessment should be halted, and they should treat their low blood sugar.
It is also important to remember that a healthcare provider should always be consulted about potential adjustments to insulin sensitivity factor.
How is insulin affected by type 1 and type 2 diabetes?
The two main types of diabetes affect insulin in different ways.
Type 1 diabetes
People with type 1 diabetes are unable to produce insulin to regulate their blood sugar levels. In people with type 1 diabetes, the beta cells that make insulin are destroyed.
People with type 1 diabetes need to take insulin every day to control their blood sugar levels.
What causes this is not known, but it is thought that at least in some cases the body's immune system mistakenly attacks and destroying the beta cells in the pancreas that produce the hormone.
According to the American Diabetes Association, around 5 percent of people with diabetes have this form of the condition. Although type 1 diabetes can occur at any age, it usually develops in childhood or young adulthood.
The symptoms of type 1 diabetes start to appear more quickly than other types of diabetes, as more and more insulin-producing beta cells are destroyed, and include:
People with type 1 diabetes need to take insulin on a daily basis to control their blood sugar levels because they have lost the ability to produce the hormone naturally. Insulin can be injected using a syringe or a continuous-release insulin pump. Insulin is required for normal body functions, so daily injections are needed for life.
Checking blood sugar levels regularly and keeping them under control using insulin also helps reduce the risk and slow the progression of complications associated with diabetes, including:
- Eye damage
- Foot problems
- Heart and blood vessel disease
- Kidney disease
- Diabetic ketoacidosis, a condition where the body breaks fat down as a source of fuel
- Nerve damage
Type 2 diabetes
Type 2 diabetes is a metabolic condition in which the body is unable to produce enough insulin, or is unable to use effectively the insulin it has produced. The condition where the body is unable to use effectively the insulin it produces is called insulin resistance.
The International Diabetes Federation estimate that up to 90 percent of the 371 million people around that world with diabetes have this form of the disorder. They also estimate that around half are unaware that they have the condition.
People with type 2 diabetes are advised to manage their blood sugar with diet and exercise, with medications added as needed to keep levels within target.
However, the progression of type 2 diabetes and the requirement for medication can often be avoided, or at least delayed. People can prevent the disease if the condition is identified at an early stage and treated with dietary measures and exercise.
The risk factors for developing type 2 diabetes include:
- Being overweight or obese
- Being physically inactive
- Having high blood pressure, high triglycerides (fats in the blood), or low "good cholesterol" levels
- Having a close relative with type 2 diabetes
It has also been found that African Americans, Mexican Americans, American Indians, Pacific Islanders, Native Hawaiians, and people of South Asian descent are more likely to develop type 2 diabetes than other people. This suggests that genes could play a role in the development of the condition.
Do insulin sensitivity factor calculations work for type 2 diabetes?
Insulin sensitivity factor can only be effectively assessed for people with type 1 diabetes who no longer produce insulin.
People with type 2 diabetes may still produce some amounts of insulin in their pancreases, and so their insulin sensitivity factor cannot be calculated reliably. People should be sure to talk to their doctor to find out what is best for them.
In people with type 2 diabetes, diet and lifestyle changes are initially recommended to lower blood sugar levels. These are followed by medications such as metformin, which works by reducing the amount of glucose released into the bloodstream and makes the body's cells more responsive to insulin.