He is suffering from diabetes mellitus
because in this disease the level of glucose is increase and in sugar glucose is present so doctor advice him of diet without sugar
and insulin help to decrease the level of glucose in the body so doctor give him injection of insulin.

Diagnosis: Diabetes
The patient in question is likely suffering from diabetes. The doctor has advised the patient to go on a diet without sugar and take insulin injections to manage the condition effectively.

Explanation:
Diabetes is a chronic medical condition that affects the body's ability to regulate blood sugar levels. There are two main types of diabetes: type 1 and type 2.

1. Type 1 Diabetes: This is an autoimmune disease where the immune system mistakenly attacks and destroys the insulin-producing cells in the pancreas. As a result, the body cannot produce enough insulin, which is necessary for the uptake of glucose by the cells. People with type 1 diabetes require insulin injections to ensure adequate blood sugar control.

2. Type 2 Diabetes: This type of diabetes occurs when the body becomes resistant to the effects of insulin or doesn't produce enough insulin to maintain normal blood sugar levels. Type 2 diabetes is often associated with lifestyle factors such as obesity, poor diet, and lack of physical activity. In some cases, oral medications may be prescribed to manage blood sugar levels. However, insulin injections may also be necessary if oral medications are not sufficient.

Reasons for the advice:
1. Diet without sugar: Sugar is a source of carbohydrates that can quickly raise blood sugar levels. By eliminating sugar from the diet, the patient can better control their blood sugar levels. This involves avoiding sugary drinks, desserts, and processed foods that contain added sugars. Instead, the patient should focus on consuming whole foods, including lean proteins, healthy fats, and complex carbohydrates from fruits, vegetables, and whole grains.

2. Insulin injections: Insulin is a hormone that helps regulate blood sugar levels by facilitating the uptake of glucose into cells. In cases where the body does not produce enough insulin (type 1 diabetes) or does not effectively use the insulin it produces (type 2 diabetes), insulin injections are necessary to maintain normal blood sugar levels. Insulin injections are typically administered through subcutaneous injections using a syringe, pen, or insulin pump.

By following a diet without sugar and taking insulin injections, the patient can effectively manage their diabetes and prevent complications associated with uncontrolled blood sugar levels. It is important for the patient to closely monitor their blood sugar levels, follow the prescribed treatment plan, and regularly consult with their healthcare provider to ensure optimal management of their condition.