Glucose 101

Glucose is a key fuel source in the body. Understanding how it is used and stored can help you make sense of the changes you see in the Levels app.

What is glucose?

Glucose (a type of sugar) is a primary energy source.
When carbohydrates are digested, glucose enters the bloodstream and moves into the body’s tissues.
Glucose eventually enters cells, where it helps power cellular processes.

Other macronutrients that can provide energy include:

Fat
Exogenous ketones (consumed rather than produced internally)
Protein
- Protein can be used for energy, but it must first be broken down into amino acids.
- The liver can convert amino acids into glucose if needed.

Your body can produce energy in different ways depending on intensity:

Long-duration, low-intensity activity (including normal daily life)
- Energy is produced from glucose and fat via aerobic respiration.
- This process is slower, but very efficient.
- It requires oxygen.
High-intensity activity
- Energy can be produced more rapidly from glucose via anaerobic respiration.
- This process is less efficient, but very fast.
- It does not require oxygen.
- It releases lactic acid as a byproduct.

When a cell’s energy needs are met, a limited amount of additional glucose is converted into glycogen.
Glycogen is stored in muscle and liver tissue.

If glucose from food is not available when energy needs increase:

Muscle glycogen can be broken down into glucose for use in the muscles themselves.
Liver glycogen can be broken down into glucose and released into the blood to fuel other tissues, including the brain.

In an average 150 lb person:

Glucose can change due to:

A Stelo biosensor or a continuous glucose monitor (CGM) measures glucose in interstitial fluid (the fluid between cells).
Interstitial glucose can lag slightly behind blood glucose.