X
More than 60,000 patients use Brite
4.6 stars
Your health finally understandable with Brite
Enter email and you're done. No subscription, no credit card.
Search, tap and you're done. Over 3,400 medicines.
Check, remind, get an overview.
Sarah K., 34
I finally understand my therapy. The app reminds me, answers my questions — and I don't feel alone with it anymore.
Insulin is vital for people with type 1 diabetes and, for many with type 2 diabetes, the next step when tablets are no longer enough. About 8 million people in Germany live with diabetes, more than one in ten adults (a German figure, broadly similar across Western countries). The most important safety topic stays the same across all insulin types: low blood sugar — fast-acting sugar belongs within reach with any therapy.
See more detail.gif)
With every insulin therapy, always keep fast-acting sugar within reach. Never leave out insulin on your own (above all with type 1 diabetes). With severe low blood sugar or ketoacidosis, call the emergency services immediately (112; or 999/112 in the UK). Last updated: May 2026.
Insulin is not a single medication, but a group of preparations with different effect profiles. Below are the most important key facts for a quick orientation; the individual points are explained in detail in the following chapters.
| Property | Details |
|---|---|
| Active substance | Insulin — the body's own hormone; therapeutically as human insulin or insulin analogues |
| Important preparations (a selection) | Basal: Lantus, Toujeo, Levemir, Tresiba, Insuman Basal — bolus: NovoRapid, Humalog, Apidra, Fiasp, Actrapid — mixed: NovoMix, Humalog Mix |
| ATC code | A10A |
| Substance class | Insulins and analogues |
| Mechanism of action | Promotion of the glucose uptake from the blood into the body cells → lowering of the blood sugar |
| Administration | Subcutaneous injection with a pen, syringe, or insulin pump — never into the muscle |
| Therapy regimens | Basal-bolus (ICT), conventional with mixed insulin, basal-supported (BOT), insulin pump (CSII) |
| Storage | Supply at 2–8 °C in the fridge, do not freeze; an opened pen mostly 4 weeks at room temperature |
| Most important risk | Low blood sugar (hypoglycaemia) — always keep fast sugar within reach |
| With type 1 | Vital — never leave out |
| Prescription status | Yes |
| Most important note | Diabetes education as a foundation — rotate injection sites, know the sick-day rules |
Insulin is a vital hormone that is normally formed in the pancreas and lowers the blood sugar. With diabetes, this regulation is disturbed — either insulin is missing entirely (type 1 diabetes) or it no longer works sufficiently (type 2 diabetes). Then insulin must be supplied from outside, mostly through an injection under the skin.
Insulin is not a single active substance, but a group of preparations with different effect profiles — from ultra-fast-acting insulins for eating to long-acting basal insulins for the basic supply. This variety makes it possible to adjust the therapy individually to the daily routine and the needs.
Insulin is a highly effective medication and, for many people, vital — but it requires knowledge and care. The most important safety topic is low blood sugar (hypoglycaemia), which can quickly become dangerous and which every insulin user must be able to recognise and treat. The right injection technique, the adjustment to meals and exercise, and the storage are also decisive. This article explains the basics in a practical way.
Insulin is the "key" that lets the sugar from the blood into the body cells. After eating, the blood sugar rises — insulin ensures that the glucose is taken up from the blood into the cells (above all muscle, fat, and liver cells), where it is used as energy or stored. Thereby the blood sugar sinks to a healthy level.
Insulin has further metabolic effects beyond this: it inhibits the new glucose formation in the liver, promotes the storage of energy (as glycogen and fat), and influences the protein metabolism. With insulin deficiency, the body cannot use the sugar — the blood sugar rises dangerously, while the cells "starve" and the body switches to an emergency metabolism (ketone formation).
Important for the use: since injected insulin lowers the blood sugar, its amount must match the food intake and the need. Too much insulin (or too little food, a lot of exercise) leads to low blood sugar, too little insulin to high blood sugar. To steer this balance is the core of the insulin therapy — and the reason why education and self-management are so important.
With type 1 diabetes, the immune system destroys the insulin-producing cells of the pancreas — the body produces no own insulin any more. Insulin from outside is here vital and must be supplied for a lifetime. Without insulin, a life-threatening metabolic derailment occurs.
With type 2 diabetes, the own insulin at first works worse (insulin resistance), later the production also declines. Many people with type 2 diabetes manage for a long time with lifestyle measures and tablets such as metformin. Insulin is used when these are no longer sufficient to set the blood sugar well — often in more advanced stages.
Insulin can also be necessary with gestational diabetes (when nutrition is not enough), with certain operations, severe diseases, or particular metabolic situations. The doctor sets the indication and the therapy regimen individually.
A central topic for the understanding of the insulin therapy. The insulins differ above all in how fast they work and how long the effect lasts. That determines when and for what they are used:
| Insulin type | Onset of effect | Duration of effect | Use |
|---|---|---|---|
| Ultra-short-acting analogues (NovoRapid, Humalog, Apidra, Fiasp) | A few minutes | about 2–4 hours | With meals (bolus) — directly before or with eating |
| Short-acting human insulin / regular insulin (Actrapid, Insuman Rapid) | about 30 minutes (an injection-eating gap necessary) | about 4–6 hours | With meals — with a waiting time before eating |
| Long-acting basal insulins (Lantus, Toujeo, Levemir, Tresiba) | Evenly after several hours | Up to 24 hours or longer | Basic need (basal) — mostly 1–2× daily |
| Mixed insulins (NovoMix, Humalog Mix, Insuman Comb) | A combined onset (a short + a long share) | Several hours | Simplify the use — fewer injections, but less flexible |
Which insulin is used in which regimen depends on the diabetes type, lifestyle, everyday life, and individual factors. It is important to know one's own insulin and its effect profile — above all the onset of effect (for the timing before eating) and the effect maximum (for the risk of low blood sugar).
There are various therapy regimens that use insulin in different ways — depending on the diabetes type, lifestyle, and individual need:
| Regimen | Principle | Advantages and disadvantages |
|---|---|---|
| Basal-bolus (intensified insulin therapy, ICT) | Long-acting basal insulin + with every meal short-acting bolus insulin matching the carbohydrate amount | Very flexible, the standard with type 1 — several injections and blood sugar measurements daily, good education necessary |
| Conventional therapy with mixed insulin | Mixed insulin mostly 2× daily | Simpler, fewer injections — fixed eating times and amounts necessary |
| Basal-supported oral therapy (BOT) | Long-acting basal insulin (mostly in the evening) in addition to diabetes tablets | An entry into the insulin therapy with type 2 — simple, well steerable |
| Insulin pump (CSII) | A continuous short-acting insulin delivery as a basal rate + bolus doses at the push of a button | Very fine steering, often combined with CGM — above all with type 1; technical care necessary |
The correct injection technique is decisive for a reliable effect. Insulin is injected under the skin (subcutaneously) into the subcutaneous fatty tissue — not into the muscle:
The exact technique is conveyed individually in the diabetes education. Errors in the technique (e.g. injecting into the muscle, into hardened tissue, or pulling out too fast) can strongly change the insulin uptake and lead to fluctuating blood sugar values.
A practically very important point that is often underestimated. Insulin is injected at various body sites — and the regular rotation of the injection site is essential:
| Injection site | Uptake speed | Preferred for |
|---|---|---|
| Abdomen | Fastest uptake | Short-acting insulin (bolus with meals) |
| Thigh | Slower uptake | Long-acting basal insulin |
| Buttocks | Slower uptake | Long-acting basal insulin |
| Upper arms | Medium uptake | Both insulin types possible |
The rotation of the injection sites is one of the simplest and most effective measures for a stable blood sugar setting — and is often neglected in everyday life.
The most important safety topic of the insulin therapy. A low blood sugar (hypoglycaemia) arises when the blood sugar drops too strongly — mostly through too much insulin, too little or too late food, unaccustomed physical exertion, or alcohol. It can quickly become dangerous and must be treated immediately.
Every insulin user — and their surroundings — should know the warning signs and always keep fast-acting sugar within reach. Repeated low blood sugars should be discussed medically (therapy adjustment).
The counterpart to low blood sugar: with too little insulin (e.g. a forgotten injection, an infection, defective insulin) the blood sugar rises too strongly (hyperglycaemia). Unlike low blood sugar, it mostly develops more slowly, but with a strong derailment is likewise dangerous.
