Type 1 and Type 2 Diabetes Mellitus: What's the Difference

Diabetes mellitus (DM) is a chronic disease that develops when the hormone insulin does not work properly. Insulin is needed to deliver glucose (sugar) from the blood into cells to produce energy.

Although both types of diabetes lead to high blood sugar levels (hyperglycemia), the causes and mechanisms underlying their development are fundamentally different.

Here are the main differences between type 1 and type 2 in simple terms.

1. Type 1 Diabetes Mellitus (Insulin-Dependent)

What happens?
A person's immune system mistakenly attacks and destroys the cells of the pancreas (beta cells) that produce insulin. As a result, the pancreas stops producing insulin entirely.

Key characteristic:Absolute insulin deficiency.

• Age of onset:More common in children, adolescents, and young adults (but can occur at any age).

• Cause:Genetic predisposition + a viral infection or another trigger (an autoimmune process).

• Body weight:Usually lean or normal weight.

• Symptoms:Appear abruptly, suddenly. Intense thirst, frequent urination (including at night), rapid weight loss, weakness, fruity (acetone) breath odor.

• Treatment:Lifelong insulin injections only. Pills will not help because the body produces no insulin of its own.

• Ketoacidosis:High risk. Without insulin, the body starts burning fat and producing toxic ketone bodies (acetone) — a life-threatening condition.

2. Type 2 Diabetes Mellitus (Non-Insulin-Dependent)

What happens?
The pancreas works (especially in the early stages) and produces insulin, but the body's cells lose sensitivity to it. This is called insulin resistance. The pancreas tries to compensate by producing more insulin than normal, but over time it becomes exhausted.

Key characteristic:Relative insulin deficiency (there is plenty of insulin, but it doesn't work well).

• Age of onset:Usually after 40–45 years (recently becoming more common in younger people, but still rare in children).

• Cause:Sedentary lifestyle, obesity, poor diet, genetic predisposition.

• Body weight:More often overweight or obese (80–90% of cases).

• Symptoms:Develop gradually, over years. Often asymptomatic at first. Thirst, itchy skin, frequent infections, fatigue, slow wound healing.

• Treatment:Begins with diet, exercise, and pills (metformin, etc.). With long-term progression, insulin may also be required.

• Ketoacidosis:Rare (possible only in the terminal stage when the pancreas is exhausted).