Where does the glucose in your blood come from?

The glucose in your blood comes from the carbohydrates in your food. Carbohydrates include sugar and starchy foods such as bread, pasta and rice. When you eat, the carbohydrates pass from your stomach into your small intestines. The carbohydrates are then broken down into glucose. Your body converts some of the glucose into a chemical called “glycogen”, which it stores in your liver and muscles. The remaining glucose will travel through the bloodstream to fuel your body’s cells and organs. This is the glucose you are measuring when you self-test your blood glucose level. Your brain and the cells in your body need the energy from glucose to function, so it is important that your blood glucose level is within a healthy range.

During a meal and for the following two to three hours, the carbohydrates in your food will be used to fuel your cells and body. After this, the carbohydrate part of the meal is used up and your blood glucose level starts to drop. Your liver then converts its glycogen stores back into glucose and sends it into your bloodstream. If you haven’t eaten for a long time and your glycogen stores have run out, your body converts its fat and protein stores into glucose. This process is called “gluconeogenesis”.

Therefore there are three ways that glucose gets into your blood:

Your bloodstream’s main source of glucose is from the carbohydrates that you eat.
Your body converts some of the glucose from the carbohydrates you eat into a chemical called glycogen, which it stores in your liver. If your blood glucose level falls too low, your liver will convert the glycogen back into glucose and send it into your bloodstream to boost your blood glucose level.
When there isn’t a supply of carbohydrate from your diet and your glycogen stores have run out, your blood glucose level drops. Your body will then convert its fat and protein stores into glucose using a process called “gluconeogenesis”.