Type 1 diabetes is a chronic autoimmune disease in which the body's own immune system destroys the insulin-producing beta cells in the pancreas. Without beta cells, the body can generally no longer produce insulin — and without insulin, glucose (sugar) cannot get from the blood into the cells, where it is needed as energy.
Insulin may never be stopped on one's own
Without an insulin supply from outside, type 1 diabetes is generally life-threatening. Those affected mostly have to supply insulin for life — via an insulin pen or insulin pump. Always discuss changes to the therapy regimen with the diabetes team.
No fault — an autoimmune disease
Type 1 diabetes is NOT caused by lifestyle, diet or "too much sugar". It is an autoimmune disease that can in principle affect anyone.
In Germany, around 341,000 adults and about 37,000 children and adolescents live with type 1 diabetes. Each year about 4,000 children and adolescents are newly affected; the numbers have been rising slightly for years.¹˒⁵
2. Difference from type 2
Feature
Type 1 diabetes
Type 2 diabetes
Cause
An autoimmune disease — absolute insulin deficiency
Insulin resistance + relative insulin deficiency
Age
Mostly childhood/adolescence; can occur at any age (LADA too)
Often middle or older age
Lifestyle
Not caused by lifestyle
Often in combination with excess weight
Insulin
Generally required for life
Initially lifestyle/tablets; insulin mostly only in later stages
A type 1 diabetes generally does not develop overnight. The autoimmune process often begins years before the first symptoms. Since the approval of teplizumab, this knowledge is for the first time therapeutically relevant too.⁶
Stage 1Autoimmunity — still normal blood sugar
At least two typical autoantibodies against beta cells are detectable in the blood (e.g. GAD-Ab, IA-2-Ab, ZnT8-Ab, IAA). The blood sugar is still normal, generally no symptoms are present. The lifetime risk of transitioning to stage 3 is considerably increased in this group.
Stage 2Dysglycemia — blood sugar abnormal, but not yet diabetes
Autoantibodies are positive AND the blood sugar is already abnormal (e.g. impaired glucose tolerance) — but there is not yet a manifest diabetes. Mostly still no symptoms.
Teplizumab can intervene here
In this phase, according to the prescribing information, teplizumab can delay the transition to stage 3 by an average of about two years.⁶
The classic symptoms appear — strong thirst, frequent urination, weight loss. From this point on, a lifelong insulin therapy is generally necessary. In a relevant portion of children, the first manifestation shows itself as ketoacidosis (emergency — see section 5).
Early detection programs
Programs such as the Fr1da study in Germany or the European EDENT1FI project test children for autoantibodies in order to recognize stage 1 and 2 — and to be able to intervene early in the future.
4. Causes and risk factors
Genetic predisposition
Certain HLA genes (among others HLA-DR3 and DR4) increase the risk for a type 1 diabetes. When a parent is affected, there is a moderately increased risk for the children. In identical twins the concordance is considerably higher. Nevertheless, the predominant part of new cases occurs in families without a known type 1 diabetes.¹
Autoimmune process
The immune system forms autoantibodies against the beta cells — this process often begins as early as toddler age and can be detectable years before the first symptoms. Typical autoantibodies: GAD-Ab, IA-2-Ab, ZnT8-Ab and IAA. They serve as early markers and are a prerequisite for a possible teplizumab therapy.⁶
Possible triggers
Viral infections (among others enteroviruses) are discussed as possible triggers of the autoimmune process
Further environmental factors (e.g. vitamin D status, food proteins in infancy) are being researched — the data is so far inconsistent
Cannot be influenced: type 1 diabetes can neither be prevented nor caused by diet or movement
5. Symptoms and a ketoacidosis warning
With type 1, the symptoms generally develop considerably faster than with type 2 diabetes — often within days to weeks:
When insulin is lacking, the body falls back on fat as a source of energy. In the process, ketone bodies arise that make the blood acidic (acidosis). In a relevant portion of children, a type 1 diabetes is only diagnosed in the context of a ketoacidosis.¹
nausea, vomiting, abdominal pain
a fruity-sweet smell on the breath (acetone)
deep, fast breathing (Kussmaul breathing)
clouding of consciousness up to a coma
Ketoacidosis — call 112 immediately! (in the US: 911)
A ketoacidosis is a medical emergency. In children with thirst, frequent urination and weight loss, the blood sugar should generally be measured promptly.
6. Diagnosis
The diagnosis is generally made via a combination of the clinical picture and laboratory values:
Fasting blood sugar ≥ 126 mg/dl (7.0 mmol/l) or random blood sugar ≥ 200 mg/dl with typical symptoms¹˒⁷
HbA1c ≥ 6.5% as the "long-term blood sugar". Note: with a very rapid onset the HbA1c can still be normal
Autoantibodies (e.g. GAD-Ab, IA-2-Ab, ZnT8-Ab) — mostly positive with type 1, generally negative with type 2
C-peptide — low or barely measurable with type 1 (no own insulin); with type 2 mostly normal or elevated
Do not overlook LADA
In adults with a first manifestation, the determination of the autoantibodies is generally important — otherwise a LADA (Latent Autoimmune Diabetes in Adults) can be wrongly classified as type 2.
Without insulin, type 1 diabetes cannot be treated. Which insulin regimen, which dose and which type of insulin are used in the individual case is always decided by the treating diabetes team.¹
Basal insulin (long-acting insulin)
Covers the basic need over the day and during the night. Active ingredients: e.g. insulin glargine, insulin degludec, insulin detemir. NEW: Insulin icodec has been available in the EU since 2025 for the first time as a basal insulin that is injected only once per week — the areas of use are currently being discussed in the guidelines.
Bolus insulin (mealtime insulin)
Is generally used at mealtimes. The concrete dose depends on the amount of carbohydrates and the current blood-sugar value (individual training necessary). Examples: insulin lispro, insulin aspart, insulin glulisine.
Intensified conventional therapy (ICT) — the basal-bolus principle
A combination of basal and bolus insulin. Considered the standard of modern type 1 therapy and requires structured training: measuring blood sugar, estimating carbohydrates (carb/bread units) and calculating corrections.¹
Insulin pump therapy (CSII)
A small pump continuously delivers insulin via a catheter. The basal rate runs in the background, the mealtime bolus is delivered at the push of a button. Pumps are frequently used in Germany particularly in children and adolescents. Tubeless patch-pump systems (e.g. Omnipod 5) are stuck directly onto the skin.
Never stop insulin on your own
Not even with illness, little appetite or "good" values. Without insulin, a life-threatening ketoacidosis threatens within a few hours. Always discuss changes to the therapy regimen with the diabetes team. More: Stopping medications.
8. Modern technology: CGM and AID systems
Continuous glucose monitoring (CGM)
A CGM sensor is attached under the skin and measures the tissue sugar every 1–5 minutes. The values are sent wirelessly to the smartphone. CGM has considerably changed type 1 therapy in recent years.¹
Often no routine finger pricks needed anymore
trend arrows show whether the sugar is rising, falling or stable
alarms can warn of low or high blood sugar — at night too
Follow function: relatives can follow along with the values remotely (e.g. parents of children with type 1)
AID systems combine a CGM sensor, an algorithm and an insulin pump: the sensor measures, the algorithm calculates, the pump delivers the adjusted dose. Mealtime insulin is mostly still entered manually — hence "hybrid".
Study data 2025: AID improves outcomes
Study data (among others Karges et al., Lancet Diabetes & Endocrinology, 2025) show under AID therapy more time in the target range, more rarely severe hypoglycemia and often a better HbA1c than under purely manual therapy.³ According to the German guideline, an AID system should be offered when an ICT with CGM does not reach the therapy goals.
System
Manufacturer
CGM compatibility
Special features
MiniMed 780G
Medtronic
Guardian 4 / Simplera Sync
Fully automatic correction bolus
t:slim X2 + Control-IQ
Tandem
Dexcom G6/G7
Sleep and activity mode
Omnipod 5
Insulet
Dexcom G6/G7
Tubeless patch-pump system; from 2 years
mylife Loop + CamAPS FX
Ypsomed
Dexcom G6/G7
CamAPS FX on iPhone too; from 1 year
Table scrollable to the right
9. NEW: teplizumab (Teizeild) — delaying type 1 diabetes
EU approval on January 8, 2026 — available in Germany since February 16, 2026
With teplizumab, for the first time a medication is available that, according to the current data, can delay the outbreak of a type 1 diabetes in a narrowly defined patient group in stage 2.
Teplizumab (Teizeild) — an anti-CD3 antibody
What: A monoclonal antibody that binds to the CD3 receptor on T lymphocytes and can intervene in the autoimmune process For whom: According to the EU approval, for adults and children from 8 years with type 1 diabetes in stage 2 — i.e. at least two autoantibodies positive AND abnormal blood-sugar values (dysglycemia), but not yet a manifest diabetes⁶ Efficacy (TN-10 study, n=76): a delay of the transition to stage 3 by a median of around 2 years. At the end of the study: ~57% of the teplizumab group still in stage 2 vs. ~28% under placebo⁶ Application: A single treatment cycle with daily intravenous infusions over 14 days. After that, generally no further administration. Exclusively in specialized centers. Side effects: Frequently temporary lymphopenia, leukopenia and a skin rash. Rarely: cytokine release syndrome. Regular laboratory checks prescribed. Manufacturer: Sanofi. In the USA approved as Tzield since 2022.
Important: not a cure — only for stage 2
Teplizumab does NOT cure a type 1 diabetes and generally does not permanently prevent the outbreak — it can delay the transition to stage 3 on average. The medication is exclusively approved for stage 2, not with an already manifest type 1 diabetes. The prerequisite is an early detection through autoantibody screening.
10. Living with type 1 diabetes
Diet: A special "diabetic diet" is generally not necessary — what is decisive is to estimate the carbohydrates of a meal and to adjust the insulin accordingly (after medical training). Fiber-rich foods often let the blood sugar rise more slowly.
Sport: Physical activity is generally possible with type 1 and is often recommended. Important: good planning, measuring blood sugar before sport, taking in carbohydrates if applicable, adjusting the insulin dose, keeping quickly available carbohydrates ready for an emergency.
Alcohol: Alcohol can lower the blood sugar — the risk of nighttime hypoglycemia can be increased. More: Medications and alcohol.
Travel: Transport insulin cool (not frozen!); a sufficient reserve, a multilingual medical certificate for insulin, injections, the pump and the CGM. More: Medications when traveling.
Driver's license and occupation: Type 1 diabetes is generally not a fundamental obstacle. A blood-sugar check before starting to drive and quickly available carbohydrates are customary. Special regulations apply for certain occupations.
Emergency management
With warning signs of hypoglycemia (trembling, sweating, a racing heart, ravenous hunger): immediately take in fast carbohydrates, measure again after a few minutes. With severe hypoglycemia with unconsciousness: call 112 (in the US: 911) and — if trained — apply a glucagon emergency medication (e.g. as a nasal spray). Never put anything into the mouth of an unconscious person. With suspicion of ketoacidosis likewise immediately 112 (in the US: 911).
11. Type 1 diabetes in children
Type 1 diabetes is among the most common metabolic diseases in childhood and adolescence.⁵
Often a sudden onset; in a relevant portion the disease is only diagnosed in the context of a ketoacidosis
insulin pumps and AID systems are widespread in childhood in Germany; Omnipod 5 is approved from 2 years, CamAPS FX from 1 year
CGM is generally considered the standard in this age group; the follow function makes it possible for parents to follow along with the values
structured training for children AND parents is important — estimating carbohydrates, dosing insulin, recognizing hypoglycemia
in the daycare center or school, emergency medications (e.g. glucagon) and fast carbohydrates should be within reach; the educational staff should be informed
in puberty the metabolic control can mostly become more difficult — hormonal fluctuations and psychological strain play a role here
psychological strain and eating disorders (e.g. "diabulimia") should be discussed early with the diabetes team
NEW: with a familial predisposition, an autoantibody screening can make sense — in rare cases a therapy with teplizumab comes into question in stage 2⁶
How brite helps you with type 1 diabetes
brite brings structure to your diabetes therapy — from basal insulin to the diabetologist's appointment.
Intake reminder — basal insulin, bolus insulin, the CGM sensor change, the pump-set change: brite reminds you reliably. Set up a reminder
Interaction check — check insulin in combination with other medications (e.g. cortisone can raise the blood sugar) for free. Check now
Health history — document blood sugar, HbA1c, hypoglycemia, sensor days and symptoms in a structured way. Track your history
Digital medication plan — the insulin regimen, CGM, pump and further medications clearly organized for the diabetologist, GP and emergency room. Go to medication plan
According to the current state of knowledge, type 1 diabetes is generally not curable — those affected mostly need insulin for life. Teplizumab (Teizeild) can delay the outbreak in a narrowly defined group in stage 2 by an average of about two years, but does not cure it. Research on further approaches (e.g. beta-cell regeneration) is ongoing.⁶
Teplizumab is the first antibody approved in the EU (approval on January 8, 2026, available in Germany since February 16, 2026) that can delay the outbreak of a type 1 diabetes in stage 2. Approved for children from 8 years and adults with demonstrated autoantibodies AND abnormal blood-sugar values, but not yet a manifest diabetes. The therapy consists of a single 14-day treatment cycle with daily infusions in a specialized center.⁶
In most cases yes. With modern therapy (insulin, CGM, AID systems) a largely normal life is mostly possible — including sport, travel and many occupations. The technical possibilities have developed considerably in recent years.¹
The combination of a CGM sensor, an algorithm and an insulin pump. The algorithm automatically adjusts the insulin dose at short intervals to the current glucose value. Mealtime insulin is generally still entered manually — hence "hybrid". Current systems in Germany: MiniMed 780G, Omnipod 5, t:slim X2 with Control-IQ and mylife Loop with CamAPS FX.¹
With warning signs, immediately take in fast carbohydrates (e.g. glucose, a sugary drink), wait a few minutes and measure again. With severe hypoglycemia with unconsciousness: emergency number 112 (in the US: 911) and — if someone in the surroundings is trained — apply a glucagon emergency medication. Never put anything into the mouth of an unconscious person.
Yes — sport is generally possible with type 1 and is often recommended. Important are planning, an adjusted insulin dose and quickly available carbohydrates. AID systems often offer special activity modes. The fine-tuning should always happen together with the diabetes team.
LADA (Latent Autoimmune Diabetes in Adults) is a form of autoimmune diabetes that only occurs in adulthood and at first often looks like a type 2 diabetes. Typical are detectable autoantibodies in mostly slim patients without pronounced insulin resistance. Differentiation via the determination of autoantibodies and C-peptide.
This should be discussed in the individual case with the pediatrician or a diabetological outpatient clinic — especially with first-degree relatives with type 1 diabetes. Programs such as the Fr1da study offer free tests in part. Since the approval of teplizumab, early detection has for the first time a possible therapeutic consequence.⁶
S3-Leitlinie Therapie des Typ-1-Diabetes (DDG, AWMF Reg-Nr. 057-013, 2023). awmf.org
Deutsche Diabetes Gesellschaft (DDG): Gesundheitsbericht Diabetes und Factsheet. ddg.info
Karges B. et al.: Hybrid closed-loop systems and hypoglycaemia risk in young people with type 1 diabetes — Lancet Diabetes & Endocrinology (2025). dzd-ev.de
diabinfo.de — Informationen zu Typ-1-Diabetes (DZD/HMGU/DDZ). diabinfo.de
Robert Koch-Institut: Nationale Diabetes-Surveillance — Daten zu Kindern und Jugendlichen. diabsurv.rki.de
Nationale VersorgungsLeitlinie Typ-2-Diabetes (ÄZQ/AWMF, Dez. 2024) — ergänzend zu Diagnosekriterien. awmf.org
Medical disclaimer: This article is for general information and does not replace medical advice, diagnosis or therapy. Insulin dosages, the choice of the insulin regimen, the indication for a pump or AID therapy as well as the decision about teplizumab are always determined individually by the treating diabetes team. With suspicion of a ketoacidosis (a fruity-sweet smell on the breath, vomiting, deep fast breathing, clouding of consciousness) or with severe hypoglycemia, call 112 immediately (in the US: 911). Insulin may generally never be stopped on one's own. Last updated: April 2026.
