Basal Insulin: Long Acting Insulins in Diabetes Mellitus Overview
The term basal insulin does not refer to a single substance but rather to a class of longer acting insulin preparations that cover the constant baseline insulin requirement. They suppress hepatic glucose production during fasting periods between meals and overnight, maintaining fasting blood glucose within the target range. Basal insulins, together with mealtime insulins, form intensified insulin therapy (ICT) in type 1 diabetes and are a central component of many treatment models in type 2 diabetes.
Currently four main groups are available in Germany: NPH insulin (delayed by binding to protamine sulfate), glargine (Lantus, Toujeo, Abasaglar, Semglee), detemir (Levemir), and degludec (Tresiba). The choice of basal insulin depends on action profile, hypoglycemia risk, lifestyle, and cost effectiveness. Therapy is a highly personal matter because efficacy, tolerability, and daily routine must be individually coordinated.
Mechanism of Action and Insulin Types
All insulins bind to the insulin receptor on muscle, fat, and liver cells, promoting glucose uptake and inhibiting hepatic glucose production. The classes differ mainly in their formulation, that is, in their duration of action and action profile.
NPH Insulin (intermediate acting): Onset of action after 1 to 2 hours, maximum after 4 to 6 hours, duration of action 12 to 16 hours. Usually requires two daily injections and shows a pronounced nocturnal peak with increased hypoglycemia risk.
Glargine U100 and U300: Forms microprecipitates in subcutaneous tissue from which insulin is released gradually. Duration of action approximately 22 to 26 hours with U100, up to 36 hours with U300, largely without a pronounced peak.
Detemir: Binds reversibly to albumin via a fatty acid side chain and delays absorption. Duration of action 12 to 24 hours, often two injections required.
Degludec: Forms stable multihexamers in subcutaneous tissue from which monomers are released slowly. Duration of action over 42 hours, very flat profile, one injection per day, highest flexibility in injection timing.
Applications
- Type 1 Diabetes mellitus: Mandatory component of intensified insulin therapy (basal insulin plus mealtime insulin)
- Type 2 Diabetes mellitus: When oral antidiabetic agents and/or GLP 1 receptor agonists fail, usually started with one basal insulin injection at night (basal supported oral therapy, BOT)
- Gestational diabetes: When dietary measures are insufficient; NPH insulin and detemir are better documented in pregnancy
- Secondary diabetes due to pancreatic disease, steroid therapy, after pancreatic surgery
- Hospital care: Conversion from insulin pumps or during surgery
Dosage and Administration
BOT in Type 2: Initially 10 units of basal insulin in the evening or 0.1 to 0.2 IU/kg, stepwise adjustment by 2 units every three days until fasting blood glucose is within target range (typically 100 to 130 mg/dl or 5.6 to 7.2 mmol/l).
ICT in Type 1: Basal rate comprises approximately 40 to 50 percent of daily insulin requirement, with the remainder going to mealtime insulin. Total daily requirement in adults is usually between 0.5 and 1.0 IU/kg, considerably lower with physical activity.
Pen administration: Rotate daily injection sites (abdomen, thigh, buttocks, upper arm) to avoid lipohypertrophy. Pen needles are single use products and should be changed after each injection to prevent infection and dosing inaccuracy.
Storage: Unopened pens in refrigerator at 2 to 8 degrees Celsius, currently used pen at room temperature (maximum 25 degrees Celsius, 4 to 8 weeks depending on preparation). Do not freeze, do not expose to direct sunlight.
Side Effects
Common: Hypoglycemia (especially at night and early morning), weight gain (4 to 6 kg in first months is typical), lipohypertrophy at repeatedly used injection sites, fluid retention.
Occasional to rare: Allergic reactions local or systemic, transient vision disturbances at start of therapy due to osmotic lens changes, paradoxical worsening of peripheral neuropathy at start of intensified therapy, lipoatrophy.
Important, severe hypoglycemia: Sweating, tremor, confusion, loss of consciousness. Patients on insulin should carry emergency glucose gel or dextrose. Glucagon emergency injection (intramuscular, intranasal Baqsimi) available for caregivers in case of severe hypoglycemia.
Drug Interactions
- Oral antidiabetic agents (Metformin, SGLT2 inhibitors, sulfonylureas, GLP 1 RA): Additive blood glucose reduction, often desired, reduce insulin dose accordingly
- Beta blockers (especially non selective): Mask hypoglycemia warning symptoms, prolong hypoglycemia
- Glucocorticoids: Substantially increase insulin requirement, especially with pulse therapy
- Alcohol: Inhibits gluconeogenesis, severe delayed hypoglycemia possible, especially with exercise or fasting
- Pentamidine, Octreotide, Lanreotide: Affect insulin secretion and glucose homeostasis
- Diuretics and atypical antipsychotics: Increase insulin requirement through insulin resistance
Special Precautions
Pregnancy: NPH insulin and detemir have the longest clinical experience. Glargine is considered safe, degludec is increasingly well documented in studies. Insulin requirement increases significantly in second and third trimester. Close diabetes management by an interdisciplinary team is standard.
Surgery and acute illness: Insulin requirement can double in short term. Hospital admission for severe acute events, perioperative insulin infusion protocols are established. Patients should not drastically reduce their insulin doses independently during illness as this carries the risk of diabetic ketoacidosis.
Education: Regular structured diabetes education (DMP diabetes education in Germany) is proven to be the most important factor for good insulin therapy. Topics include correct pen operation, carbohydrate counting, correction factor, exercise, alcohol, and travel.
Glucose monitoring: Continuous glucose monitoring (CGM) and flash glucose monitoring (FGM, for example Freestyle Libre) are now standard in ICT therapy and are reimbursed by health insurance when requirements are met.
You might also be interested in
- Insulin Glargine, long acting basal insulin
- Metformin, oral first line therapy in type 2
- Empagliflozin, SGLT2 inhibitor
- Semaglutide, GLP 1 receptor agonist
- Glucagon, emergency therapy for severe hypoglycemia
Frequently Asked Questions
Which basal insulin is the best?
This cannot be answered in general terms. Glargine U300 and degludec significantly reduce the risk of nocturnal and severe hypoglycemia compared to NPH and glargine U100 in studies, but are more expensive. NPH is cost effective but has stronger action profiles with nocturnal peak. Selection depends on hypoglycemia tendency, lifestyle, and comorbidities; the decision is made by the team of diabetology practice and patient.
Why am I gaining weight on insulin?
Insulin is anabolic and promotes storage of glucose, fat, and protein. During insulin therapy, the previously untreated glucose loss through urine is often corrected (approximately 200 to 400 kcal per day), increasing energy balance. Structured nutrition, physical activity, and combination with metformin or GLP 1 RA can reduce this effect.
How do I recognize severe hypoglycemia?
Early signs are sweating, trembling, intense hunger, irritability, concentration problems. At values below 50 mg/dl, confusion, seizures, and loss of consciousness threaten. Take fast carbohydrates (15 g dextrose or juice) immediately, measure again after 15 minutes. In case of loss of consciousness, caregivers should administer glucagon or call emergency number 112.
Can I skip my basal insulin if I am fasting?
No, basal insulin covers the nutrition independent baseline insulin requirement. During prolonged fasting (Ramadan, preoperative fasting), the dose is individually adjusted, often reduced by 10 to 30 percent, but not stopped completely. Discuss the approach in advance with your diabetology practice.
Sources
- German Diabetes Society DDG, Practice Recommendations
- AWMF National Care Guideline Type 2 Diabetes
- Gelbe Liste, Insulin Overview
- BfArM, Federal Institute for Drugs and Medical Devices
Legal Notice and Disclaimer
The information provided on this page is for general informational purposes only and does not constitute medical advice, diagnosis, or treatment recommendation. It does not replace the advice of a licensed physician or pharmacist. Medications should only be taken as prescribed by a physician or as dispensed by a pharmacy. All information is based on specialist information published at the time of creation and recognized scientific sources; the current manufacturer's product information is always authoritative. Sanoliste assumes no liability for completeness, timeliness, or accuracy of the information presented. In a medical emergency, call emergency number 112.