state one reason why the concentration of glucose in the blood increases.

there is an increase in the production of insulin

One reason why the concentration of glucose in the blood increases is due to the consumption of high-carbohydrate foods, such as sugary snacks or starchy meals. When we eat foods that are rich in carbohydrates, they are broken down by the body into glucose, which then enters the bloodstream for distribution to the cells as a source of energy.

To determine this answer, we can consider basic knowledge of how our body digests and processes food. When we consume carbohydrates, they are broken down into glucose through the process of digestion. This glucose is absorbed into the bloodstream from the small intestine. From there, it is transported to various organs and tissues, including the liver, muscles, and brain, to provide them with energy.

During digestion, the body tries to maintain a relatively stable concentration of glucose in the blood. However, when we consume a large amount of carbohydrates, especially simple sugars, the body may struggle to process and utilize all the glucose efficiently. This can lead to an increase in blood glucose levels, a condition known as hyperglycemia.

It's important to note that other factors, such as certain medical conditions like diabetes or hormonal imbalances, can also result in elevated blood glucose levels. In such cases, the body may have difficulty regulating and utilizing glucose effectively, causing a persistent increase in blood glucose concentration.

Since Jiskha doesn't have a biology expert at this time, please try posting your question at this site.

http://www.biology-online.org/biology-forum/

In addition, be sure to make really good use of KhanAcademy!
http://www.khanacademy.org/science/biology
Choose from the general topics at the right and then find the specifics you need within each topic.