Diabetes mellitus (diabetes), in general

Diabetes mellitus (diabetes), in general
International Classification (ICD) E14.-



Diabetes mellitus is derived from the Greek and translates to "honey-sweet flow". Diabetes is an umbrella term for metabolic diseases that are associated with hyperglycemia (elevated blood sugar).

In a healthy, fasting person, the blood glucose level is below 100 mg/dl. Postprandially (after eating) this value should rise to a maximum of 140 mg/dl. If it is exceeded, this may indicate impaired glucose tolerance (abnormal blood sugar utilisation) or diabetes mellitus. An oral glucose tolerance test (oGTT) is necessary to determine which disorder is involved.

If left untreated, the blood glucose levels in diabetes mellitus, which have been elevated for years, lead to secondary diseases. Particularly affected are:

  • Brain
  • Eyes
  • Vessels
  • Nervous system
  • Heart
  • Kidneys

Main forms of diabetes

Type 1 diabetes

A lack of insulin causes this type of diabetes. Antibodies (the body's defence system) destroy cells in the pancreas that are responsible for producing insulin. Other names for this type are "early," "juvenile," or "juvenile" diabetes, because it is the classic insulin-deficient diabetes that often begins in childhood.

Type 2 diabetes

Two factors play a role here. On the one hand, the body develops insulin resistance, and on the other hand, the producing cells are "worn out" by many years of overproduction. In the past, the term "adult-onset diabetes" was also used, as it mostly occurs in adults. Today, however, this type is also found in obese children and adolescents.

Over 90% of diabetics suffer from this form, which also occurs more frequently in families.

Type 1 diabetes Type 2 diabetes
Frequency ∼ 5% of diabetics > 90% of diabetics
Origin Autoimmune insulin deficiency Insulin resistance, impaired insulin secretion
Occurrence mostly children, adolescents mostly adults
Familial accumulation rarely frequent
Body weight mostly normal mostly overweight
Metabolism unstable stable
Therapy Lifelong insulin therapy Weight reduction, increase in activity, change in diet, oral blood sugar reducers, insulin therapy as last option

Rare forms of diabetes

Type 3 diabetes: secondary diabetes, LADA and MODY diabetes

  • Secondary diabetes - secondary disease

Trigger Description
Pancreas Pancreatitis (chronic inflammation) can lead to loss of function, main cause is alcohol abuse. If approx. 90% of the insulin-producing cells are destroyed, diabetes results.
Endocrine glands If too much thyroid hormone, growth hormone or cortisone is produced, diabetes can develop. Triggering diseases are e.g. hyperthyroidism (overactive thyroid gland), Cushing's syndrome or acromegaly (overproduction of growth hormone).
Medications Drugs can also have a diabetogenic effect, i.e. trigger diabetes. Long-term cortisone therapy, for example, can lead to exogenous Cushing's syndrome and thus diabetes. Other triggers can be thyroid hormones and diuretics (thiazide diuretics).
  • LADA Diabetes - Latent Autoimmune Diabetes of Adults is a special form of diabetes mellitus type-1. Affected individuals are between 25 and 40 years old, and their insulin-producing cells in the pancreas are attacked by antibodies. Treatment options are diet or medication.
  • MODY diabetes - Maturity Onset Diabetes oft he Young is based on rare, inherited gene defects. Young people (< 25 years) are affected, about every 100 diabetics. The course of the disease is mild, insulin production is maintained for many years.

Type 4 diabetes: Gestational diabetes

Gestational diabetes, or gestational diabetes, occurs during pregnancy as one of the most common comorbidities and usually resolves. Approximately 5% of pregnant women are affected, and they are more likely to suffer from type 2 diabetes later on.


The so-called islets of Langerhans of the pancreas produce insulin. It is needed by all cells in the body to absorb glucose from the blood and convert it into energy. If no sugar can be absorbed, the concentration in the blood increases. A permanently elevated level in turn damages sensitive cells. Depending on the type of diabetes, a distinction is made between the causes of high blood sugar levels

Type 1 diabetes

Insulin-producing cells are destroyed by their own antibodies (autoimmune). The production capacity decreases until it fails completely. The exact cause is still unclear, but genetic factors are suspected due to familial accumulation (HLA characteristics D3/D4).

Type 2 diabetes

In this type, cells have developed insulin resistance (insensitivity). Significantly more insulin is required for the same mechanism to absorb glucose. The islets of Langerhans produce more insulin to match the increased demand, causing them to overload in the long run and produce less and less.

This type of diabetes is also known as a disease of affluence, as risk factors include poor diet, obesity and lack of exercise. A link to metabolic syndrome is also often observed. Another factor may be diabetogenic drugs that interfere with glucose metabolism.

Gestational Diabetes

The delicate balance of blood sugar raising and lowering hormone insulin in the body is disturbed by pregnancy. This results in a higher demand for insulin. If this cannot be met, gestational diabetes develops.

Secondary diabetes

Insulin is the only hormone that can lower blood sugar levels, in contrast to the increase that can be triggered by many hormones. These are, for example, thyroid hormones T3 and T4, growth hormones, cortisone (cortisol) and adrenaline. If there is an imbalance between these hormones, diabetes mellitus can develop. The cause of a disturbed balance can be ingested hormones or hormone-forming tumors.

Pancreatitis (inflammation of the pancreas) or pancreatic carcinoma (cancer of the pancreas) can also be causative factors, as it is responsible for insulin production.


The following symptoms may occur in type 1 and 2:

  • Polyuria (frequent need to urinate), nocturia (need to urinate at night).
  • Polydipsia (increased thirst)
  • Lack of appetite, weight loss
  • listlessness, fatigue, lack of energy
  • Cravings (often at the onset of the disease)
  • Susceptibility to infections (urinary tract and skin infections)
  • Itching
  • Headache, dizziness
  • Nausea and even vomiting
  • Visual disturbances
  • Muscle cramps
  • Disturbed consciousness

Type 1 diabetes

Symptoms develop rapidly in days to weeks. Particularly noticeable are symptoms such as weight loss, discomfort, constant thirst, frequent urination to ketoacidosis (diabetic coma with unconsciousness).

Type 2 diabetes

Symptoms can take years to develop, which means diabetes often goes undiagnosed. Rarely, it is the secondary conditions that lead to a diagnosis of diabetes.

Typical symptoms:

  • Poor wound healing (especially on legs and feet).
  • Retinopathy (declining eyesight)
  • Polyneuropathy with tingling or numbness in legs (nerve damage)
  • Heart attack

Gestational diabetes

The symptoms are usually inconspicuous, diabetes is detected during routine examinations of pregnant women.


For diagnosis, the measurement of fasting blood glucose (sugar concentration in the blood) and glucose tolerance (with oral glucose tolerance test - oGTT) are necessary.

For a definite diagnosis, elevated values must be detected on at least 2 different days, regardless of age and sex.

Normal impaired glucose tolerance Diabetes
Fasting glucose

< 100 mg/dl

< 5.6 mmol/l

≥ 100 - < 126 mg/dl

5.6 - < 7.0 mmol/l

≥ 126 mg/dl

≥ 7.0 mmol/l

Value after glucose administration

< 140 mg/dl

< 7.8 mmol/l

≥ 140 - 200 mg/dl

≥ 7.8 - < 11.1 mmol/l

≥ 200 mg/dl

≥ 11.1 mmol/l

In the past, urinary sugar was also measured, but this is no longer relevant as blood glucose measurement is by far more accurate. If diabetes mellitus is diagnosed, the following examinations are subsequently carried out in order to be able to detect secondary diseases at an early stage:

  • Ocular fundus
  • Kidney values
  • Blood lipid values
  • Nerves
  • Urine
  • Blood pressure
  • Feet

Results should be included in the health passport without gaps.

Precursors of diabetes

When fasting blood glucose is between 100 and 126 mg/dl, it is called impaired fasting glucose (IFG). This may be a precursor to diabetes.

The 2-hour value on an oral glucose tolerance test should be below 140 mg/dl. However, if it is between 140 and 200 mg/dl, it is called impaired glucose tolerance (IGT), which can be a precursor to diabetes mellitus. With proper lifestyle intervention, type 2 diabetes can be prevented.


The treatment strategy depends entirely on the type of diabetes.

Type 1 diabetes

This type of diabetes can only be treated with insulin, as insulin deficiency is its cause.

Type 2 diabetes

The basic pillars of therapy in this case are a change in diet and regular physical exercise with the aim of normalising weight. Only if these measures are not effective, blood sugar-lowering medication and, as a last option, insulin are used.

Gestational diabetes

Stable blood sugar levels are particularly important for the unborn child. Blood sugar that is too high or too low can cause damage. If a change in diet is not sufficient, insulin is given. Medication is not an option in this case, as it would harm the unborn child.

Secondary diabetes

First, it is important to treat the triggering disease. If this is successful, the diabetes will also disappear on its own.

Monitor therapy

The long-term blood glucose (HbA1c) is used to check how successful the blood glucose control of the last 3 months has been.

Control examinations (routine and annual examinations) are carried out by the family doctor and/or the diabetes outpatient clinic. They are particularly important to determine any secondary diseases and the success of treatment. The following aspects are examined or discussed:

  • HbA1c values (in the blood)
  • Blood sugar
  • Optimisation of diet and exercise behaviour
  • Blood pressure
  • Weight
  • Blood fat values (cholesterol, triglycerides, etc.)
  • Kidney values (creatinine, urea)
  • Salt values in the blood (sodium, potassium)
  • Sugar and protein excretion (microalbuminuria)
  • Ocular fundus
  • Feet (vibration sense, foot pulses)

Results should be recorded in the diabetes health passport.


  • Self-help is very important in the treatment of diabetes. However, teaching and experience are prerequisites for this.
  • In the "Diabetes School", information about diabetes is taught by experts in one week.
  • Self-help groups help with experience.
  • Learn to determine and assess your blood sugar yourself. This enables you to control the therapy yourself in everyday life.
  • If you have to inject yourself with insulin, detailed instructions are important.
  • Only through regular check-ups can secondary diseases be detected and treated as quickly as possible.
  • Foot care is very important. Avoid even the smallest injuries and disinfect every wound immediately.


Forms 1 and 2 cause secondary diseases if blood sugar is poorly controlled. Continuously high blood sugar damages blood vessels and leads to arteriosclerosis (hardening of the arteries).

The following diseases are threatening with badly controlled diabetes:

  • Heart attack (4-fold increased risk)
  • Heart failure (5-fold increased risk)
  • Stroke (3-fold increased risk)
  • Kidney disease (diabetic nephropathy in 25% of diabetics after 10 years)
  • Eye disease (diabetic retinopathy in 90% of type 1 and 25% of type 2 diabetics after 15 years)
  • Nerve damage (diabetic polyneuropathies in 50% of all diabetics after 10 years)
  • Diabetic foot syndrome (2-10% of all diabetics)

The risk decreases with better blood sugar control. On the basis of the HbA1c value, the blood glucose level of the last weeks can be largely reconstructed. Blood pressure also played a role in the prevention of further diseases.

The development of secondary diseases usually takes several years. However, if diabetes itself is discovered late, further complications may already exist at diagnosis.

A normal life expectancy is possible with optimal treatment.


Type 1 diabetes

Since it is an autoimmune disease without any external factors involved, this type cannot be prevented.

Type 2 diabetes

The clear causes of this disease of affluence are obesity and lack of exercise. Prevent this diabetes by eating a varied and balanced diet and getting enough exercise. This is especially important if you have diabetics in your family.

Gestational diabetes

Being overweight increases the risk of gestational diabetes. That's why a healthy diet and exercise are important. Try to eat enough, but not "for 2". Other influencing factors such as familial clustering cannot be counteracted.

Precursors of diabetes

Impaired fasting glucose or glucose tolerance does not definitely lead to diabetes. Those who know they have a precursor can help maintain stable blood glucose levels with exercise, a healthy diet, and weight loss if they are overweight. Usually these measures are enough to prevent diabetes, as well as vascular disease, etc.

Editorial principles

All information used for the content comes from verified sources (recognised institutions, experts, studies by renowned universities). We attach great importance to the qualification of the authors and the scientific background of the information. Thus, we ensure that our research is based on scientific findings.
Danilo Glisic

Danilo Glisic

As a biology and mathematics student, he is passionate about writing magazine articles on current medical topics. Due to his affinity for facts, figures and data, his focus is on describing relevant clinical trial results.

The content of this page is an automated and high-quality translation from DeepL. You can find the original content in German here.



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