From lipodystrophy to subcutaneous insulin depots: Overlooked mechanisms of glycemic variability in patients with diabetes

Table 1 Ultrasound grading of lipohypertrophy lesions and suggested clinical considerations

Grade	Ultrasound imaging characteristics	Suggested clinical considerations
Grade 0	Normal (no nodules or diffuse areas)	Continue routine site rotation education and periodic site checks
Grade 1	Diffuse hyperechogenic areas without clear nodules	Avoid repeated injections into the same area; reinforce rotation and needle single-use; consider ultrasound mapping if glycemia remains unstable
Grade 2	Nodules 1-5.9 mm (width at widest point)	Avoid injecting into lesion; monitor closely when switching to unaffected tissue because absorption may increase; reinforce education and rotation
Grade 3	Nodules 6-9.9 mm	As Grade 2, with heightened vigilance and closer monitoring during site change in patients with prior hypoglycemia/Large dose requirements
Grade 4	Nodules ≥ 10 mm	Strictly avoid injections into lesion; lesions may persist longer and require sustained site avoidance and monitoring; consider follow-up ultrasound in selected patients

This table was conceptualized and synthesized by the authors based on references[2,8,11,12,14,20,21].

Table 2 Standardized procedures and safe injection techniques for the prevention of lipohypertrophy

Phase	Key actions	Core principles
Preparation and insulin handling	Storage and temperature	If insulin has been refrigerated, allow it to reach room temperature by leaving it out of the refrigerator for 30 to 60 minutes before injection; injecting cold insulin can be painful and may contribute to lipodystrophy
	Resuspension of cloudy insulin	For insulin suspensions (e.g., NPH), gently roll/tip the vial or pen to resuspend the insulin; avoid vigorous shaking to reduce air bubbles
	Priming (pen devices)	Prime the pen before injection and confirm flow by seeing insulin at the needle tip to help ensure accurate dose delivery
	Needle length	Prefer 4-mm pen needles for most people to support reliable subcutaneous delivery and reduce intramuscular injection risk
Injection technique	Choose appropriate skin area	Use clean, intact skin and avoid injecting into areas with lipodystrophy, scars, bruising, infection, inflammation, edema, or ulceration
	Angle and skinfold	With a 4-mm pen needle, inject perpendicularly (90°). A skinfold may be required for very young children and very thin adults, particularly when longer needles are used
	Delivery and needle dwell time	Inject insulin steadily and, after completing the injection, wait 10 seconds before withdrawing the needle to reduce leakage and ensure full dose delivery
	Avoid injection through clothing	Do not inject through clothing, because it prevents appropriate site inspection and can interfere with correct technique
	Needle reuse	Use needles once only; avoid reuse to reduce tissue trauma and the risk of lipohypertrophy
Site rotation	Spacing between injections	Inject at least 1 cm from the previous injection site (approximately one adult finger width) and rotate in a consistent direction
	Separate sites for concurrent injections	If two injections are given at the same time (e.g., basal and prandial insulin), administer them at separate injection sites
	Zone-based rotation	Change the body zone used for injections regularly (e.g., use one quadrant/half per week) to avoid overuse of a single area
Monitoring and early detection	Routine inspection and palpation	Visual inspection and palpation of injection sites should be performed routinely as part of patient self-check and/or by healthcare professionals; review site rotation practices at least annually
	Triggered assessment (warning signs)	Injection sites should be examined carefully when warning signs occur, including unusual pain, insulin leakage, bleeding/bruising, increased force required to deliver insulin, or glucose becoming unstable/unpredictable despite the usual regimen

Compiled by the authors based on FITTER Forward expert recommendations[14] and consistent with foundational FITTER principles[13]. NPH: Neutral Protamine Hagedorn.