Type 2 diabetes mellitus

What type 2 diabetes is

Every cell in the body needs glucose (sugar) as fuel. Glucose comes from food and from the liver, circulates in the blood and enters cells with the help of insulin, a hormone made by the pancreas. In type 2 diabetes two things combine: cells respond poorly to insulin (insulin resistance), so the pancreas has to make more and more; and over the years the pancreatic cells that make insulin become exhausted and can no longer cope with this load. The result is that glucose stays in the blood instead of entering cells.

This process is slow and often begins years before diagnosis, through an intermediate stage called prediabetes, when sugar is higher than normal but still below the threshold for diabetes. Prediabetes is the best opportunity for action, because lifestyle changes can prevent or markedly delay diabetes.

Type 2 diabetes is far more common than type 1 (an autoimmune disease in which the pancreas makes no insulin) and affects mainly adults, although it is appearing more often at younger ages, alongside rising obesity. Risk factors are age, family history, overweight (especially fat around the waist), inactivity, prediabetes, diabetes in pregnancy, polycystic ovary syndrome, high blood pressure, high cholesterol and fatty liver (hepatic steatosis).

Symptoms

In the early stages diabetes often causes no symptoms at all and can go unnoticed for years; it is found by chance on a blood test. When sugar rises a lot, the following appear:

• increased thirst and frequent urination, including at night;
• fatigue and heavy sleepiness;
• blurred vision;
• wounds that heal slowly and repeated infections (skin, urinary, genital);
• unexplained weight loss, in advanced cases;
• numbness or burning in the feet and hands.

The absence of symptoms does not mean there is no damage: complications can begin while the patient feels well. For this reason checking blood sugar is recommended for people with risk factors even without complaints.

How the diagnosis is made

The diagnosis is based on blood tests. The accepted criteria are:

• fasting glucose (after 8 hours without food) ≥ 126 mg/dl (7.0 mmol/L);
• glycated hemoglobin (HbA1c) ≥ 6.5%, which reflects average blood sugar over the last 2–3 months;
• glucose 2 hours after drinking 75 g of glucose (the oral glucose tolerance test) ≥ 200 mg/dl;
• random glucose ≥ 200 mg/dl with classic symptoms.

Without symptoms, the diagnosis is confirmed by repeating the test (or with a second test). Fasting glucose of 100–125 mg/dl and HbA1c of 5.7–6.4% indicate prediabetes. After the diagnosis the doctor asks for additional tests: a lipid profile, kidney function (creatinine, eGFR and urine albumin, see kidney tests), liver enzymes, and as needed an ECG and examination of the eyes and feet.

Why it matters: complications

High blood sugar over the years damages the walls of blood vessels, small and large, as well as nerves. This explains why diabetes affects almost every organ:

• heart and arteries: heart attack, stroke and disease of the leg arteries; diabetes roughly doubles cardiovascular risk (see diabetes and the heart);
• kidneys: diabetic nephropathy, the most common cause of chronic kidney failure;
• eyes: diabetic retinopathy, which can lead to loss of vision;
• nerves: neuropathy, with numbness, burning, pain in the feet and reduced sensation, which brings a risk of unnoticed wounds and of “diabetic foot”;
• infections that are more frequent and harder to clear.

The good news is that controlling sugar, blood pressure and cholesterol sharply lowers the risk of all these consequences.

Treatment

Treatment has four pillars that work together:

Lifestyle. This is the foundation at every stage. A balanced diet with vegetables, legumes, whole grains, and less simple sugar, sweet drinks, bread and processed products; regular physical activity (at least 150 minutes a week of moderate activity); and weight loss when overweight. A loss of 5–10% of body weight markedly improves sugar control, and large weight loss can put diabetes into remission in some patients, particularly when the diagnosis is recent. Stopping smoking is just as important.

Medicines for blood sugar. Treatment usually starts with metformin, which lowers glucose production by the liver and improves sensitivity to insulin. Today there are also drugs that, besides lowering sugar, directly protect the heart and kidneys and help with weight loss, such as SGLT2 inhibitors and GLP-1 agonists; the doctor chooses according to your conditions (heart failure, kidney disease, coronary disease, overweight) and tolerance. When these are not enough, other drugs or insulin are added; insulin is not a “failure” but a normal part of treatment when the pancreas can no longer keep up.

Controlling other risk factors. Blood pressure (the target is usually below 130/80 mmHg if tolerated), cholesterol (statins are recommended for most patients with diabetes; see dyslipidemia) and, when indicated, aspirin or other protective drugs according to risk. See also diabetes and blood pressure and diabetes and cholesterol.

The HbA1c target. It is set individually. For most adults the aim is about 7%; a stricter target (about 6.5%) is chosen when it can be reached without hypoglycemia, while in older, frail people or those with severe illness a gentler target (7.5–8%) is safer.

Hypoglycemia and emergencies

Very low blood sugar (hypoglycemia, usually below 70 mg/dl) can occur with insulin or some tablets (such as sulfonylureas). Signs are shakiness, cold sweats, hunger, a fast heartbeat, irritability and confusion. The simple rule: if you are awake and can swallow, take 15 g of fast-acting sugar (for example a glass of fruit juice, 3–4 glucose tablets or a spoonful of honey), repeat the measurement after 15 minutes and, once it passes, eat something. If the person cannot swallow or loses consciousness, call 127. On the other hand, very high sugar with vomiting, abdominal pain and rapid breathing may be ketoacidosis or a hyperosmolar state, which need hospital care.

Follow-up and check-ups

Diabetes is followed regularly, not only when there are complaints. A typical plan:

• HbA1c every 3 months when the target has not been reached or treatment has been changed, and at least every 6 months when stable, or sooner when the doctor considers it reasonable;
• blood pressure at every visit and weight;
• once a year: creatinine with eGFR and urine albumin, a lipid profile, an eye examination by an ophthalmologist (with fundus exam), a foot examination (pulses, sensation, skin) and cardiovascular assessment (see cardiology consultation);
• daily foot care: check the skin, wear suitable shoes, do not walk barefoot.

Self-monitoring with a glucose meter is used as your doctor advises, mainly when taking insulin or when there is a risk of hypoglycemia. During an acute illness with fever, vomiting or diarrhea, contact your doctor, because some medicines must be paused temporarily (for example metformin and SGLT2 inhibitors) and sugar needs more attention. Women with diabetes who are planning a pregnancy should contact their doctor before becoming pregnant.

This information is educational and does not replace a medical visit.

When to see a doctor

• fasting glucose above 100 mg/dl on a test;
• overweight and diabetes in the family, even without complaints;
• thirst, frequent urination, fatigue or blurred vision;
• wounds that do not heal, numbness or pain in the feet;
• immediately, if blood sugar is very high together with vomiting, drowsiness or rapid breathing.