This composite clinical photograph illustrates two types of cutaneous allergic reactions to subcutaneous insulin administration in a patient with type 2 diabetes. Panel A shows a generalized urticarial reaction on the abdominal wall surrounding the umbilicus. Visually, this is characterized by multiple raised, pale-pink wheals of varying sizes and shapes, with some appearing confluent, surrounded by diffuse erythema (flares). The morphology is typical of a Type I hypersensitivity reaction. Panel B demonstrates a localized cutaneous reaction on the upper right thigh at an injection site. This milder presentation consists of localized erythema and slight edema; a specific point of interest is demarcated with a blue ink circle to highlight the injection site reaction. These images serve as educational visual aids for identifying common dermatological manifestations of insulin allergy, ranging from widespread urticaria to localized injection-site swelling and erythema.

A multi-modal educational visual comparing the subcutaneous distribution of injected insulin. The left panel shows a histological cross-section (light microscopy/immunohistochemistry) of adipose tissue. The dermis is visible as the superior layer, while the injected insulin is stained red, demonstrating its distribution within the fat lobules and the formation of a localized depot. The right panel displays a segmented 3D tomographic reconstruction from an X-ray CT scan of a similar injection. This 3D model illustrates the irregular, somewhat spherical morphology of the injection depot, the vertical injection channel created by the needle, and backflow at the skin surface. The contrast in the CT scan is achieved using an iodine-based agent mixed with the drug. Scale bars of 1 mm are present in both images. This comparison is used to study tissue mechanics, drug delivery patterns, and the localized pressure effects of subcutaneous injections in pharmaceutical research.

This clinical photograph illustrates a patient self-administering medication, specifically an insulin injection, using an insulin pen device. The image shows a woman in a clinical setting at the Rainbow Specialist Medical Center, focusing on the manual dexterity and technique required for subcutaneous injection in the abdominal region. The patient is holding a blue-capped insulin delivery device with both hands, positioned against the abdomen. The clinical environment is evidenced by the presence of a medical examination table with blue draping, anatomical models (a heart model), and clinical documents in the background. This visual serves as an educational example of diabetes self-management, patient education, and the use of medical devices in a real-world primary care or specialist setting. The photograph emphasizes the practical aspect of chronic disease management and the importance of patient autonomy in endocrinology and metabolic health.

A clinical photograph depicting a laboratory setup for an in vivo cancer research procedure. The image shows an operator performing a subcutaneous injection into the mammary fat pad of a light-colored laboratory mouse. The mouse is positioned on its back on a green surgical drape, held securely by a gloved hand and specialized forceps for precision. A 1 ml insulin syringe with a fine-gauge needle is visible at the injection site. The procedural environment includes five blue-capped centrifuge tubes arranged in a row and three sterile, individually wrapped insulin syringes with orange caps to the right. This visual demonstrates the methodology for tumor cell inoculation, specifically Triple-Negative Breast Cancer (TNBC) cell lines like MDA-MB 231, to establish animal models for oncological study. The use of aseptic technique, including gloves and drapes, is evident, highlighting the standard protocol for laboratory animal interventions in biomedical research.

This clinical photograph displays a side-by-side comparison of insulin-induced lipohypertrophy on the abdominal wall of a patient with diabetes. Panel (a) illustrates the macroscopic appearance of the abdomen, showing moderate, generalized swelling and a rounded contour below the umbilicus, consistent with a localized accumulation of subcutaneous fat ('skin plate') at a frequent insulin injection site. Panel (b) demonstrates the clinical 'pinch test' for diagnostic assessment. The left side shows a significantly thicker, denser fold of tissue when the lipohypertrophic area is squeezed, while the contralateral side, where injections are avoided, results in a normal, markedly thinner skin fold. These visual findings emphasize the importance of injection site rotation to prevent abnormal adipose tissue proliferation. The images serve as an educational tool for healthcare professionals and patients to identify lipohypertrophy through inspection and palpation, highlighting the morphological differences between pathological and healthy subcutaneous tissue.

This image depicts a clinical photography of a subcutaneous injection being administered with a disposable pen-type injector. The device features a dose dial and a plunger, with a yellow indicator visible near the advance mechanism. A clinician or patient stabilizes the skin with the non-dominant hand by pinching subcutaneous tissue, while the dominant hand positions and depresses the plunger to deliver medication into the adipose layer. The needle enters the skin at a near perpendicular angle (approximately 90 degrees) to deposit the drug into subcutaneous fat for slower absorption. The abdomen is a common site for injections, but other practical regions include the outer thigh or upper arm; site rotation is advised to minimize lipohypertrophy and ensure consistent pharmacokinetics. After needle insertion and dose delivery, the device is withdrawn and the skin is gently blotted to reduce bleeding. The procedure emphasizes correct technique, avoiding intramuscular injection, excessive tissue compression, or needle bending. This image is a useful educational resource for medical trainees, diabetic patients, and healthcare professionals to practice safe subcutaneous administration, review needle depth and angle, and reinforce dose accuracy and device function. The DermNet watermark indicates dermatology education and skin-focused clinical documentation.

This diagnostic image consists of axial T1-weighted MRI cross-sections of the bilateral thighs, illustrating medication-induced lipohypertrophy. The image is divided into two comparative panels: Phase 1 (injection site: abdomen) and Phase 2 (injection site: anterior thighs), demonstrating the local adipose tissue response to Pegvisomant therapy. Quantitative annotations show measurements of subcutaneous fat thickness and overall thigh circumference. In Phase 1, subcutaneous fat thickness ranges from 17.10 mm to 28.53 mm. In Phase 2, following the change of the injection site to the thighs, there is a visible and measurable increase in subcutaneous fat, with values reaching up to 34.07 mm. Total thigh circumference also demonstrates an increase, with Phase 2 measurements (63.20 mm - 63.70 mm) exceeding those in Phase 1 (59.30 mm - 63.20 mm). The central muscle mass and femoral cortical bone remain largely unchanged, emphasizing that the hypertrophy is localized to the subcutaneous adipose layer. This comparison illustrates the reversibility and site-specific recurrence of lipohypertrophy associated with growth hormone receptor antagonist injections.

Examples: <table><thead><tr><th colspan="2">Basal-bolus regimen with insulin Optisulin (glargine) as basal insulin</th></tr></thead><tbody><tr><td>Usual insulin regimen</td><td>Humalog™ 8 units before breakfast<br>Humalog™ 6 units before lunch<br>Humalog™ 10 units before dinner<br>Optisulin™ 24 units before bedtime</td></tr><tr><td>For day of bowel preparation</td><td>Withhold Humalog™<br>Optisulin™ ½ x 24= 12 units before bedtime</td></tr></tbody></table>

Table 1- Definitions of common terms used in the guideline <table><thead><tr><th>Terminology</th><th>Definition</th></tr></thead><tbody><tr><td>Basal insulin</td><td>The role of basal ('background') insulin is to keep blood glucose levels at consistent levels between meals and during periods of fasting.<br>In people using insulin injections, basal insulin is the intermediate or long acting insulin that is administered once or twice a day to provide for the basal insulin requirements of a patient with diabetes.<br>Insulin glargine (Optisulim™, Toujeo™, Semglee™),<br>Insulin detemir (Levemir™).<br>In people using subcutaneous insulin pump therapy, basal insulin rates are programmed into the pump.</td></tr><tr><td>Intermediate-acting insulin</td><td>Basal insulin with a shorter duration of action than long-acting insulin, e.g. isophane insulin (Protaphane™, Humulin NPH™).</td></tr><tr><td>Bolus insulin</td><td>Insulin given 10-15 minutes before meals to cover the meal carbohydrate content or for correction of hyperglycaemia.<br>Ultra-rapid-acting (e.g. fast acting insulin aspart-FiAsp™),<br>Rapid-acting (e.g. insulin lispro - Humalog™, insulin aspart - Novorapid™, insulin glulisine - Apidra™) or<br>Short-acting (e.g. regular insulin: Actrapid™, Humulin R™).</td></tr><tr><td>Basal-bolus regimen</td><td>An insulin regimen consisting of basal insulin and multiple daily bolus insulin.</td></tr><tr><td>Pre-mixed insulin</td><td>Single injectable insulin that consists of a mixture of an intermediate-acting insulin and a short acting or rapid acting insulin at a pre-determined fixed ratio.<br>Examples of this would be Novomix™ 30, Mixtard™ 30/70, Humalog Mix™ 25.</td></tr><tr><td>Co-formulated insulin</td><td>Single injectable insulin that consists of a combination of an ultra-long-acting insulin and a rapid acting insulin at a pre-determined ratio.<br>Ryzodeg™ 70/30</td></tr><tr><td>Major surgery</td><td>Surgical cases requiring more than one night of hospitalisation post-operatively.</td></tr></tbody></table>

An anatomical diagram titled 'INSULIN ACTION IN THE BRAIN' illustrating the distribution of insulin receptors (IRs) and the physiological effects of insulin in the human central nervous system. The left side of the diagram features a sagittal section of the brain with yellow points indicating regions of high IR concentration, including the neocortex, hippocampus, basal ganglia, hypothalamus, olfactory areas, amygdala, choroid plexus, and cerebellum. An arrow points from this anatomical model to a list on the right, which outlines the multi-faceted roles of central insulin action. Key functions identified include the modulation of glucose metabolism, mobilization of GLUT4 transporters, and regulation of peripheral metabolism. The diagram also highlights insulin's impact on neuroplasticity and maintenance, specifically synaptic plasticity, neurogenesis, neurite outgrowth, neuroprotection, and the modulation of memory and cognition. Additionally, it notes insulin's role in oligodendrocyte health (proliferation, differentiation, and myelination) and the control of glial function. This educational infographic is designed to demonstrate the critical importance of insulin signaling for cognitive activity and neurological homeostasis.