Together, insulin and glucagon help maintain a state called homeostasis in which conditions inside the body remain steady. When blood sugar is too high, the pancreas secretes more insulin. When blood sugar levels drop, the pancreas releases glucagon to raise them.
This balance helps provide sufficient energy to the cells while preventing the nerve damage that can result from consistently high levels of blood sugar.
In this article, we explain the functions and processes of insulin and glucagon as well as their effects on diabetes.
Insulin, glucagon, and blood sugar
Insulin and glucagon affect how the body manages blood sugar levels.
The body converts the carbohydrates from food into glucose, a simple sugar that serves as a vital source of energy.
Blood sugar levels are a measure of how effectively the body uses glucose.
These vary throughout the day. However, in most instances, insulin and glucagon keep these levels within a healthy range.
When the body does not convert enough glucose, blood sugar levels remain high. Insulin helps the cells absorb glucose, reducing blood sugar and providing the cells with glucose for energy.
When blood sugar levels are too low, the pancreas releases glucagon. Glucagon instructs the liver to release stored glucose, which causes blood sugar to rise.
Islet cells in the pancreas are responsible for releasing both insulin and glucagon. The pancreas contains many clusters of these cells. There are several different types of islet cell, including beta cells, which release insulin, and alpha cells, which release glucagon.
How insulin works
The cells need glucose for energy. However, most of them are unable to use glucose without the help of insulin.
Insulin gives glucose access to the cells. It attaches to the insulin receptors on cells throughout the body, instructing the cells to open up and grant entry to glucose.
Low levels of insulin constantly circulate throughout the body. A spike in insulin signals to the liver that blood glucose is also high. The liver absorbs glucose then changes it into a storage molecule called glycogen.
When blood sugar levels drop, glucagon instructs the liver to convert the glycogen back to glucose, causing blood sugar levels to return to normal.
Insulin also supports healing after an injury by delivering amino acids to the muscles. Amino acids help build the protein that is present in muscle tissue, so when insulin levels are low, muscles may not heal properly.
How glucagon works
The liver stores glucose to power the cells during periods of low blood sugar. Skipping meals and poor nutrition can lower blood sugar. By storing glucose, the liver makes sure that blood glucose levels remain steady between meals and during sleep.
When blood glucose falls, cells in the pancreas secrete glucagon. Glucagon instructs the liver to convert glycogen to glucose, making glucose more available in the bloodstream.
From there, insulin attaches to its receptors on the body's cells and ensures that they can absorb glucose.
Insulin and glucagon work in a cycle. Glucagon interacts with the liver to increase blood sugar, while insulin reduces blood sugar by helping the cells use glucose.
Ideal blood sugar levels
A range of factors, including insulin resistance, diabetes, and an unbalanced diet, can cause blood sugar levels to spike or plummet.
The standard measurement units for blood sugar levels are milligrams per deciliter (mg/dl). Ideal blood sugar ranges are as follows:
|Timing||Blood glucose level (mg/dL)|
|Before breakfast||Person without diabetes: 100 mg/dL
Person with diabetes: 70–13
|2 hours after a meal||Person without diabetes: Less than 140 mg/dL
Person with diabetes: Less than 180 mg/dL
|Bedtime||Person without diabetes: 120 mg/dL
Person with diabetes: 90–150 mg/dL
A1C is a measurement that gives a picture of average glucose levels over an extended period. A1C readings should be under 7 percent for people with diabetes and less than 6 percent for those without diabetes.
How blood sugar levels affect the body
Insulin and glucagon do not take immediate effect, particularly in people whose blood sugar levels are extremely high or low.
High blood sugar
Diabetes can cause itching.
The symptoms of high blood sugar include:
- Urinating more often than usual: The kidneys respond to high blood sugar by trying to get rid of excess glucose.
- Excessive thirst that accompanies frequent urination: The kidneys can cause dehydration and feelings of intense thirst when trying to regulate blood sugar.
- Feeling excessively hungry: High blood sugar does not directly cause feelings of hunger. However, a drop in insulin often causes hunger when it accompanies high blood sugar.
Over time, extremely high blood sugar may lead to the following symptoms:
- unexplained weight loss
- slow healing
- itchy, dry skin
- increased likelihood of infections
- fatigue or difficulty concentrating
- blurred vision
- constipation, diarrhea, or both
- erectile dysfunction
Low blood sugar
Delays between meals, poor nutrition, some diabetes medications, and certain medical conditions can cause low blood sugar.
The symptoms of low blood sugar include:
- rapid heartbeat
- tingling, particularly in the tongue, lips, arms, or legs
- hunger alongside nausea
- confusion and difficulty concentrating
Without treatment, low blood sugar can lead to seizures or loss of consciousness.
Types of diabetes
Diabetes develops either when insulin becomes ineffective or when the body cannot produce enough of it. The disease causes problems with blood sugar regulation.
There are several different types of diabetes:
Type 1 diabetes
Type 1 diabetes is an autoimmune condition that often presents at a young age. For this reason, it is sometimes called juvenile diabetes.
This type of diabetes involves attacks by the immune system on some of the insulin-secreting beta cells in the pancreas.
People with type 1 diabetes often experience very high blood sugar. Low insulin levels, however, mean that they cannot use much of the glucose in their blood.
Type 2 diabetes
People with type 2 diabetes have insulin resistance, which means that the cells do not respond properly when insulin instructs them to absorb glucose from the bloodstream.
Diabetes can develop in women who are pregnant.
Gestational diabetes is a form of diabetes that develops in some women during pregnancy.
When a woman is pregnant, the placenta that supports the developing baby might impair her body's ability to use insulin.
The result of this is insulin resistance that triggers symptoms similar to those of type 2 diabetes.
Gestational diabetes usually goes away after the baby is born. However, it is a risk factor for the later development of type 2 diabetes.
Insulin and glucagon are vital for maintaining normal ranges of blood sugar.
Insulin allows the cells to absorb glucose from the blood, while glucagon triggers a release of stored glucose from the liver.
Everyone who has type 1 diabetes and some people with type 2 diabetes will need to supplement their insulin and manage their blood sugar through diet and regular exercise.
Are there any medicines that treat diabetes by eliminating excess glucose or reducing glucagon production rather than by supplementing insulin?
There are some medicines that reduce glucose or block glucagon, but they can only supplement glycemic control and may not replace insulin.
An example is pramlintide, a medication that reduces pancreatic secretion of glucagon and which doctors may prescribe as part of the treatment for type 1 diabetes. A drug called metformin reduces the amount of sugar that the liver releases and also improves the body’s ability to respond to insulin in people with type 2 diabetes.
Sodium-glucose transport protein2 (SGLT2) inhibitors are another class of drug, and they work by influencing the kidneys to secrete more glucose. An example of an SGLT2 is canagliflozin. Remember that although there are several treatment options, everyone is different, so it is important to work with your doctor to determine the best treatment plan to control your diabetes.Alan Carter, PharmD Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.