• Both insulin and glucagon normalize blood glucose levels, but they have opposite effects.
• Both are secreted by the Islet cells within the pancreas. But glucagon is released by the alpha islet cells and insulin is released by the beta islet cells.
• Both are pancreatic endocrine hormones.

Although both insulin and glucagon are secreted by the islet cells within the pancreas, they have opposite effects.

• Glucagon treats LOW blood glucose (sugar) levels by stimulating the release of stored glucose from the liver and by stimulating the liver to make more glucose. Low blood sugar levels are also known as hypoglycemia.
• Insulin treats HIGH blood glucose levels by stimulating cells in our body to take in more glucose, where it can be used for energy. Glucose that is trapped in the bloodstream does not provide any energy. High blood sugar levels are also known as hyperglycemia.

In people without diabetes, glucagon and insulin are released by our pancreas automatically (without us even thinking about it) in response to low or high blood sugar levels.

• Glucagon is released when blood sugar levels are LOW.
• Insulin is released when blood sugar levels are HIGH.

People with type 1 diabetes do not make enough insulin to ensure their cells get the energy they need. They must inject insulin every day. They also require glucagon occasionally, if they have inadvertently injected too much insulin or their body requires more insulin due to sickness or exercise.

People with type 2 diabetes usually make some insulin, at least initially. This means they can take oral tablets that work by stimulating the pancreas to produce more insulin or help the cells uptake more glucose. With time they may require insulin injections as well. Glucagon may also be required, in case they experience low blood sugar levels because their medication dosages are too high, or they are unwell.