A person who has Diabetes has difficulty controlling the glucose levels in their blood and must take Insulin to regulate it. Which characteristic of life do they need assistance with?

Based on the given information I believe this will help:

Insulin is a hormone made by the pancreas that allows your body to use sugar (glucose) from carbohydrates in the food that you eat for energy or to store glucose for future use. Insulin helps keeps your blood sugar level from getting too high (hyperglycemia) or too low (hypoglycemia).  

If you have more sugar in your body than it needs, insulin helps store the sugar in your liver and releases it when your blood sugar level is low or if you need more sugar, such as in between meals or during physical activity.  

If your body does not produce enough insulin or your cells are resistant to the effects of insulin, you may develop hyperglycemia (high blood sugar), which can cause long-term complications if the blood sugar levels stay elevated for long periods of time.

Treatment:

People with type diabetes cannot make insulin because the beta cells in their pancreas are damaged or destroyed. Therefore, these people will need insulin injections to allow their body to process glucose and avoid complications from hyperglycemia.