GLP-1 injections and fat necrosis: what the case reports show

What just happened

A case report published in Australian Doctor describes a 53-year-old patient who developed subcutaneous fat necrosis at GLP-1 receptor agonist injection sites on the thigh and abdomen — resulting in persistent, visible depressions in the skin and tissue loss that did not resolve when injection at those sites was stopped.

GLP-1 receptor agonists are now among the most widely prescribed medicines in Australia. Semaglutide — available under the brand names Ozempic (for type 2 diabetes) and Wegovy (for weight management) — and tirzepatide (Mounjaro) are both administered as weekly subcutaneous injections. The large majority of Australians on these medications self-inject at home, often with a brief instruction session at the pharmacy when they first collect the pen.

The case adds to a small but growing body of observational reports describing injection-site complications with this drug class. These complications were well-established with insulin long before GLP-1 agonists became mainstream, but they are now appearing in a much larger population of patients injecting at home without specialist oversight.

This is not a reason to reconsider GLP-1 therapy in appropriate patients — the cardiovascular and metabolic evidence base is substantial, and the benefit-risk profile for eligible patients has not changed. But injection technique, and specifically systematic site rotation, is emerging as a clinical priority that is not consistently being communicated at the time of prescription.

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The both-and

The mechanism is the same as with insulin

Injection-site lipodystrophy — loss of subcutaneous fat at injection sites — has been documented with insulin therapy for decades. Estimates from long-term insulin studies suggest it affects up to 30–50% of patients who do not rotate sites consistently. The underlying mechanism involves repeated mechanical trauma and localised inflammatory changes at the same point in the subcutaneous fat layer, progressively damaging the adipocytes that live there.

GLP-1 receptor agonists work on an entirely different molecular pathway from insulin, but the delivery method is identical — a needle into the same layer of subcutaneous fat. A weekly injection is lower frequency than the multiple daily injections many insulin users administer, but the chronic, low-grade site trauma is the same in principle. Over months and years, returning to the same anatomical point adds up.

Fat necrosis sits at the more severe end of this spectrum: not just gradual volume loss but actual tissue death and permanent structural change. The case described in the AusDoc report involved visible cosmetic changes that persisted after injection at those sites ceased.

The uptake context matters

GLP-1 prescriptions in Australia have grown substantially over the past three years. Many patients on these medicines are not being managed through a specialist diabetes team with structured injection education — they are patients seen in general practice for weight management or metabolic health, and their injection training may consist primarily of the instruction leaflet in the box.

Site rotation is simple to teach and takes two minutes to demonstrate. But it is not self-evident. The most common failure pattern is returning to the same spot — the abdominal quadrant that is easiest to reach and most familiar — week after week without varying the precise injection point. Over months, that single spot accumulates the damage.

There is also a detection problem. A patient who notices a persistent dip in the skin may attribute it to weight loss, or simply not register it as clinically significant. Their GP, who may not routinely examine injection sites, may not ask. The connection between the skin change and injection habits may never be made at a consultation.

What this does and does not mean

This case report does not suggest GLP-1 agonists are unsafe — the evidence for their benefit in eligible patients is strong and not in question here. What it does suggest is that injection-technique counselling, which has always been included in the prescribing information for these drugs, deserves the same clinical attention as any other safety discussion at initiation.

The comparable lesson from the insulin literature took decades to become routine practice. It is worth getting ahead of the same pattern with GLP-1 agonists before the number of patients on them grows further.

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2 cents

If you are injecting a GLP-1 agonist weekly, it is worth taking sixty seconds to check your rotation practice.

Has the needle been going into roughly the same spot — the familiar patch of abdomen or the outer thigh that always works — every week? That is the pattern this case report describes. The fix is simple: use a different point each week, working systematically across your injection zones. Divide the abdomen into quadrants. Move through them. Do the same for the thighs and upper arms if you use them.

If you are not sure your technique is correct, your pharmacist can check it. If you have already noticed a persistent change in skin texture or contour at a site you use regularly — a small lump, a visible depression, an area that feels numb — stop using that site and mention it to your GP before your next dose.

For clinicians reviewing patients on GLP-1 agonists: the injection-site examination that has long been standard practice for insulin is worth extending to this class. A brief look takes thirty seconds and the finding, if there is one, is clinically actionable.

Verdict: yes — a practical safety check for anyone on a GLP-1 agonist, and a prompt for prescribers to include technique review at the next consult.

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Sources cited

1. Australian Doctor — An unexpected local effect of a GLP-1 RA (11 July 2026). https://www.ausdoc.com.au/case-report/an-unexpected-local-effect-of-a-glp-1-ra/
2. Diabetes Australia — Injection technique resources. https://www.diabetesaustralia.com.au
3. NPS MedicineWise Radar. https://www.nps.org.au/radar