If patients with type 2 diabetes mellitus do not achieve their individual target values with oral antidiabetic agents and/or GLP-1 receptor agonists, insulin therapy is required. According to the recommendations of the ADA (American Diabetes Association), basal insulin is added in addition to metformin or other antidiabetic medications.
Natural Insulin Secretion as a Model
In principle, the goal of therapy—even in type 2 diabetes—is the best possible adaptation to the physiological situation of the organism. This means that therapy, whether with oral antidiabetic drugs, GLP-1 agonists or dual GLP-1/GIP agonists (incretin mimetics), insulin, or a combination of the different medications, should ideally lead to an insulin level that corresponds to the natural secretion of insulin in a person without diabetes (Fig. DT2 2, see also “What is Diabetes”).
Fig. DT2 2: Physiological insulin secretion in a person without diabetes (dark blue: prandial insulin secretion compensating for carbohydrate intake; light blue: basal insulin secretion compensating for glucose derived from glycogenolysi
When is insulin therapy necessary in type 2 diabetes?
Insulin therapy is indicated when a person with type 2 diabetes has already reached the stage of reduced insulin secretion. In this situation, the body still produces its own insulin, but no longer in sufficient amounts to achieve a physiological insulin level (Fig. DT2 3). In addition, due to existing insulin resistance, the insulin that is present is less effective.
The therapeutic principle for achieving a blood glucose level as close as possible to the natural conditions of the organism is therefore: by using all available approaches (diet, physical activity, non-insulinotropic antidiabetic agents), insulin resistance should be minimized, and together with the administration of insulin, a physiological insulin level should be achieved. From this, the different approaches to insulin therapy are derived.
Figure DT2 3: Reduced endogenous insulin secretion in type 2 diabetes – although insulin is still present, secretion is insufficient to maintain physiological insulin levels, and its effect is further impaired by insulin resistance.
BOT in Type 2 Diabetes (Basal-Supported Oral Therapy)
In basal-supported oral therapy (BOT), a long-acting insulin is injected once daily in addition to oral antidiabetic agents or GLP-1 receptor agonists for diabetes management. In exceptional cases, a therapy with GLP-1 analogues in combination with insulin may also be considered. In principle, the long-acting insulin increases the basal, meal-independent insulin level. Most importantly, it helps to reduce elevated fasting glucose values if these persist despite ongoing treatment with oral antidiabetic agents or incretin mimetics. The insulin that covers basal requirements supports, together with non-insulin antidiabetic drugs, the effect of endogenous insulin at mealtimes (Figure DT2 4). In BOT, glucose monitoring is essential, either through self-monitoring of blood glucose or continuous glucose monitoring (CGM).
Figure DT2 4: In BOT, the basal intermediate-acting insulin administered in addition to non-insulin antidiabetic agents raises the basal insulin level. Together with non-insulin antidiabetic agents, this supports the action of endogenous insulin at mealtimes (dashed curves: physiological insulin secretion; pink: basal insulin; lighter blue: meal-independent insulin compensating for glucose derived from glycogenolysis; dark blue: meal-related insulin compensating for dietary carbohydrates).
Guidelines recommend starting with 10 IU/day or 0.1–0.2 IU/kg/day of an intermediate-acting insulin or a long-acting insulin analogue. The dose should be increased twice weekly by 10–15% or by 2 to 4 units (IU) until the fasting blood glucose target is achieved. The target for fasting blood glucose must be set individually, depending on age and comorbidities. In case of hypoglycemia, the cause should first be identified and, if possible, eliminated. If no plausible reason is found, the basal insulin dose should be reduced again by 4 units or 10–20%.
Intensification of Basal-Supported Oral Therapy (BOT)
If BOT alone does not achieve the therapeutic target, the next step according to the guidelines is the addition of a rapid-acting insulin at the main meal.
In this approach, BOT is continued, and an additional 4 units (IU), or 0.1 IU/kg, or 10% of the basal dose is administered before the main meal. If HbA1c is below 8%, a reduction of the basal insulin dose should be considered.
The dose is increased twice weekly by 1–2 units or 10–15% until the individual daily blood glucose profile target is reached.
If hypoglycemia occurs, the cause should be identified and, if necessary, the dose should be reduced by 2–4 units or 10–20%.
If the individual treatment goal still cannot be achieved with these measures, a basal-bolus therapy (BBT) should be considered.
Supplementary Insulin Therapy (SIT)
Another form of non-intensive insulin therapy is supplementary insulin therapy (SIT). In this regimen, oral antidiabetic agents/incretin mimetics are combined with short-acting insulins or insulin analogues. The latter are injected with main meals to control postprandial glucose excursions. This requires glucose monitoring in order to adjust the mealtime insulin dose (unless fixed meal plans and injection schemes are used). This form of therapy is applied in patients with type 2 diabetes who, due to declining endogenous insulin production, can no longer maintain postprandial glucose levels within target range.
Both SIT and BOT represent variants of non-intensive insulin therapy, which, with further decline in endogenous insulin production, can be expanded into intensified conventional insulin therapy (ICT) by adding further insulin injections (Figure DT2 5).
Figure DT2 5: Progression of non-intensive insulin therapy: BOT and SIT as initial strategies, which may be expanded to intensified conventional insulin therapy (ICT) through the addition of further insulin doses as endogenous insulin production decreases.
This form of therapy is now used only in exceptional cases in a small number of patients (both with type 1 and type 2 diabetes). It is mainly considered for older individuals with a regular daily routine, or for patients who require the simplest possible insulin regimen. The administration of fixed insulin doses requires a fixed dietary plan in order to maintain balance between insulin (which lowers blood glucose) and the intake of carbohydrates (bread units [BU], carbohydrate units [CU]), which raise blood glucose.
Compared to demand-adjusted intensified insulin therapy (ICT), the risk of hypoglycemia is significantly higher in CT. In addition, fixed dietary schemes and injection schedules restrict flexibility in daily life, which is a major disadvantage for still very active patients. If individual therapeutic goals cannot be achieved with conventional insulin therapy (CT), intensified insulin therapy (ICT) should be considered.
Principle of Conventional Insulin Therapy (CT)
Long-acting or intermediate-acting insulin, or mixtures of intermediate- and short-acting insulin, are injected once or twice daily in fixed ratios; in rare cases, up to three times daily.
The basal insulin dose is typically divided into two-thirds in the morning and one-third in the evening, or one-half in the morning and one-half in the evening. Basal insulin is replaced by a premixed insulin.
The dose is increased twice weekly by 1–2 units until the individual target is reached. If hypoglycemia occurs, the cause should be identified; if no plausible cause is found, the insulin dose should be reduced by 2–4 units or 10–20%.
Blood Glucose Self-Monitoring in CT
Patients on conventional insulin therapy must monitor their blood glucose themselves. They should create daily blood glucose profiles at regular intervals. Usually, one daily profile per week is sufficient. The results must be documented and presented at the next medical appointment.
There is increasing discussion about whether continuous glucose monitoring (CGM) should also be used in non-intensive forms of insulin therapy, possibly financed by self-payment.
Snacks Are Not Always Optional in CT
A disadvantage of CT is the fixed pharmacokinetic profile of the injected insulin. The dose is not adjusted, and the ratio of short-acting to long-acting insulin is predetermined (usually by the composition of the premixed insulin used). Patients must therefore strictly adhere to fixed meal sizes and timings in their daily routine. This is a major disadvantage for people with type 2 diabetes who are still working or prefer a more flexible lifestyle (Figure T2D 6).
Figure T2D 6: Insulin levels under conventional insulin therapy (CT) with twice-daily injections of premixed insulin. Food intake must be adapted to the injected insulin, requiring strict adherence to mealtimes and, among others, additional snacks. (Yellow dashed line for comparison: physiological insulin secretion in a person without diabetes). If snacks are omitted, the resulting insulin surplus poses a risk of hypoglycemia.
Insulins for Conventional Insulin Therapy (CT)
There are premixed insulins containing rapid-acting insulin analogues (e.g., NovoMix®, Humalog Mix®). These rapid-acting insulin analogues have a duration of action of approximately 2–3 hours, with a peak effect after about one hour.
Insulins are usually administered with main meals. With premixes containing rapid-acting insulin analogues, snacks are not required.
Regular human insulin has a duration of action between 4 and 6 hours, depending on the dose, with a peak effect after about 2 hours. After 2 hours, the majority of carbohydrates have already been absorbed and metabolized, yet insulin levels remain elevated. To avoid hypoglycemia, carbohydrates must therefore be ingested. Consequently, with premixes containing regular human insulin, the intake of regular snacks is usually required due to high insulin levels between meals. This, in turn, promotes weight gain.
The above recommendations for insulin therapy are adapted from the ADA guidelines:
Standards of Medical Care in Diabetes – 2024, Diabetes Care Volume 47, Supplement 1, January 2024, 9. Pharmacologic Approaches to Glycemic Treatment, pp. S158–S178
In basal-bolus therapy (BBT), patients inject a long-acting insulin to cover basal requirements. In addition, a rapid-acting insulin is injected at mealtimes. Self-monitoring of blood glucose is mandatory. In principle, BBT corresponds to intensified conventional insulin therapy (ICT).
Even in people with type 2 diabetes, BBT/ICT offers several advantages, as it is modeled on the natural physiology of the organism. As a result, blood glucose control is usually significantly better than with conventional insulin therapy (CT), which substantially reduces the risk of diabetes-related complications. Moreover, lifestyle flexibility is greatly improved, allowing patients more freedom in their diet and daily routine. For these patients, self-monitoring of blood glucose is essential, which can be achieved comprehensively and in real time with modern diabetes technology such as continuous glucose monitoring (CGM). In principle, the application of BBT/ICT requires prior structured education.
Figure T2D 7: Insulin profile under intensified conventional insulin therapy (ICT) in people with type 2 diabetes. In this regimen, short-acting insulin is injected at mealtimes (green) to supplement the insufficient endogenous insulin (dark blue). The also insufficient basal insulin level (lighter blue) is covered by intermediate-acting or long-acting insulin (pink).
In addition to the main meal, rapid-acting insulin is also administered with other meals. Therapy is initiated with 4 units (IU), 0.1 IU/kg, or 10% of the basal insulin dose before each meal. If HbA1c is below 8%, a reduction of basal insulin should be considered.
The dose is increased twice weekly by 1–2 units or 10–15% until the individual target is reached.
If hypoglycemia occurs, the cause must be identified. If no clear cause is found, the dose of the last injection before the hypoglycemia should be reduced by 2–4 units or 10–20%.
It is important to ensure that patients do not gain weight. Metformin should be continued as long as it is tolerated and no contraindications exist. Additional combinations with other oral antidiabetic agents should be determined on an individual basis. In almost all patients with type 2 diabetes, fixed insulin doses are sufficient. In overweight patients, adjusting insulin doses to carbohydrate intake is generally not necessary, as this does not usually improve glycemic control and increases the risk of weight gain. Much more important is lifelong dietary modification and sustained motivation, which can achieve far greater benefits than adapting insulin doses to carbohydrate units (CU).
Unlike in the past, type 2 diabetes is increasingly diagnosed in younger individuals who are still professionally active. In these patients, ICT is often indicated due to lifestyle and work-related factors. With CGM, therapy management is significantly facilitated, which is why its use in intensively insulin-treated patients, including this group, is reimbursed by healthcare payers [1].
The use of insulin pumps in people with type 2 diabetes—whether for manual administration (CSII, continuous subcutaneous insulin infusion) or within the framework of semi-automated hybrid insulin delivery with AID systems (AID – Automated Insulin Delivery)—is a matter of ongoing debate. The fact is that in Germany, insulin pump therapy is not reimbursed by health insurance, except in well-justified exceptional cases [2].
European Union
In many EU countries, reimbursement for insulin pumps exists — but usually under restrictive conditions (e.g., mainly for type 1 diabetes, for children, or in specific medical cases).
For people with type 2 diabetes, reimbursement by public health insurance is typically not standard and only granted in exceptional cases with strong medical justification.
In Germany, for example, insulin pump therapy can be reimbursed under statutory health insurance (mainly for type 1 diabetes), but for type 2 diabetes it usually requires a special application and medical approval.
Some EU countries maintain national lists of reimbursed medical devices, and insulin pumps are often included — but not with a broad indication for type 2 diabetes.
United States
In the U.S., reimbursement is possible through private insurers or public programs like Medicare — but not automatically for type 2 diabetes. Patients usually need to meet specific criteria (e.g., high insulin requirements, poor glycemic control despite multiple daily injections, frequent hypoglycemia).
Some insurers classify insulin pumps as “Durable Medical Equipment (DME).” If patients meet the requirements, coverage can be granted.
Medicare (for older adults and people with disabilities) may reimburse pump therapy and supplies, provided medical necessity criteria are met — again depending on diagnosis, insulin needs, and approval.
India
In India, the situation is clear: public health systems and standard insurance plans generally do not cover insulin pump therapy, whether for type 1 or type 2 diabetes.
Studies and Indian guidelines confirm that pumps are usually paid out of pocket and are not included in standard coverage.
Private insurance may sometimes cover parts of the costs (e.g., specific devices or consumables), but there is no reliable, routine reimbursement under most policies.
In people with type 1 diabetes, endogenous insulin is typically absent. Insulin pump therapy aims to mimic their physiological insulin needs as closely as possible. The key advantage of pump therapy (manual or CGM-controlled) remains basal insulin delivery.
Current AID systems are hybrid models, meaning basal insulin delivery is automated, while mealtime boluses still have to be administered manually. With such individualized basal rates, circadian rhythms can be reproduced almost exactly in type 1 diabetes. In type 2 diabetes, however, this is not necessary, as endogenous insulin is usually still present—just not in sufficient quantities (see Figure DT2 2 above).
In type 2 diabetes, endogenous insulin is still secreted according to circadian rhythm, making finely tuned basal dosing unnecessary. In principle, a cost-effective insulin pump delivering a constant basal rate would suffice to raise overall basal insulin levels (Figure DT2 8). A system such as those used in type 1 diabetes is not required in type 2 diabetes—neither for manual CSII nor for automated insulin delivery.
Figure DT2 8: Insulin levels in people with type 2 diabetes with physiological insulin deficiency. The insulin pump delivers the missing insulin as a constant basal rate (green), which elevates residual physiological insulin levels and supplements inadequate postprandial glycemia with bolus doses (dark blue complemented by green).
Are AID Systems Useful in Type 2 Diabetes?
If fully automated insulin delivery systems (AID) become available in the future, mealtime boluses would also be administered automatically. This would ensure reliable postprandial glycemia and thus provide a new rationale for their use in type 2 diabetes.
At present, the indications for hybrid AID systems in type 2 diabetes correspond to the rare cases that justify classical insulin pump therapy [3]:
Ultimately, the use of AID systems is also a question of daily treatment costs. Compared with ICT combined with CGM, costs are approximately €10/day higher (pump, reservoirs, infusion sets). Therefore, the widespread use of hybrid AID systems and manual insulin pumps for “classic CSII” in type 2 diabetes cannot currently be justified (except for self-paying patients).
Conclusion: Insulin pumps, whether applied as classical CSII or automated AID systems, remain primarily a therapeutic option for type 1 diabetes. In type 2 diabetes, their use is limited to exceptional cases with strict indications. Positive study results on AID systems (e.g., [4]) do not change this overall assessment.
An overview of current insulins can be found here in the chapter Insulins
[1] Federal Ministry of Health: Announcement of a resolution by the Federal Joint Committee on an amendment to the directive on outpatient medical care: Continuous interstitial glucose monitoring with real-time devices (rtCGM) for therapy management in patients with insulin-dependent diabetes mellitus, June 16, 2016. Federal Gazette, published by the Federal Ministry of Justice and Consumer Protection, September 6, 2016. https://www.g-ba.de/downloads/39-261-2623/2016-06-16_MVV-RL_rtCGM_BAnz.pdf?msclkid=ddce3b8ad03111ec9258e12d62f0496e. Last accessed: June 12, 2025.
[2] Socio-medical statement on the treatment of diabetes mellitus with external insulin pumps; April 2006, pp. 7f; prepared by the Socio-Medical Expert Group “Healthcare Structures” (SEG-3) of the MDK Association.
[3] Henrichs HR, Liebl A, Reichel A, Quester W, Freckmann G, Fach E-M, Thomas A on behalf of the AGDT of the DDG. Experimental investigations and clinical evidence of insulin pump therapy (CSII). Diabetologie und Stoffwechsel 2009; 4: 390–397.
[4] Pasquel FJ, Davis GM, Huffman DM, Peters AL, Parker JC, Laffel LM, Romeo GR, Mathew J, Castorino KN, Kruger DF, Dungan KM, Kipnes M, Jauch EC, Oser TK, Shah VN, Horowitz B, Carlson AL, Warren ML, Deeb W, Buse JB, Reed JH, Berner J, Blevins T, Bajaj C, Kollman C, Raghinaru D, Ly TT, Beck RW; Omnipod 5 SECURE-T2D Consortium. Automated Insulin Delivery in Adults With Type 2 Diabetes: A Nonrandomized Clinical Trial. JAMA Netw Open. 2025 Feb 3; 8(2): e2459348.
[1] Federal Ministry of Health: Announcement of a resolution by the Federal Joint Committee on an amendment to the directive on outpatient medical care: Continuous interstitial glucose monitoring with real-time devices (rtCGM) for therapy management in patients with insulin-dependent diabetes mellitus, June 16, 2016. Federal Gazette, published by the Federal Ministry of Justice and Consumer Protection, September 6, 2016. https://www.g-ba.de/downloads/39-261-2623/2016-06-16_MVV-RL_rtCGM_BAnz.pdf?msclkid=ddce3b8ad03111ec9258e12d62f0496e. Last accessed: June 12, 2025.
[2] Socio-medical statement on the treatment of diabetes mellitus with external insulin pumps; April 2006, pp. 7f; prepared by the Socio-Medical Expert Group “Healthcare Structures” (SEG-3) of the MDK Association.
[3] Henrichs HR, Liebl A, Reichel A, Quester W, Freckmann G, Fach E-M, Thomas A on behalf of the AGDT of the DDG. Experimental investigations and clinical evidence of insulin pump therapy (CSII). Diabetologie und Stoffwechsel 2009; 4: 390–397.
[4] Pasquel FJ, Davis GM, Huffman DM, Peters AL, Parker JC, Laffel LM, Romeo GR, Mathew J, Castorino KN, Kruger DF, Dungan KM, Kipnes M, Jauch EC, Oser TK, Shah VN, Horowitz B, Carlson AL, Warren ML, Deeb W, Buse JB, Reed JH, Berner J, Blevins T, Bajaj C, Kollman C, Raghinaru D, Ly TT, Beck RW; Omnipod 5 SECURE-T2D Consortium. Automated Insulin Delivery in Adults With Type 2 Diabetes: A Nonrandomized Clinical Trial. JAMA Netw Open. 2025 Feb 3; 8(2): e2459348.