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cgm side effects

CGM Side Effects and How to Avoid Them

We all experience different side effects when using a CGM (constant glucose monitor). CGM sensors are considered safe to use, but there is still a percentage of users that experience irritable side effects. In this article, we investigate what’s causing the issues and how we can avoid CGM side effects.

The science of diabetes control and glycemic index monitoring has expanded significantly to include the development of technologies leveraging the concept of continuous glucose monitoring (CGM). CGM devices like the Dexcom G7, Dexcom G6, and the FreeStyle Libre 3 use wearable glucose sensor technology to easily help patients track blood sugar levels over time. Unlike the conventional finger-blood tests, patients only need to wear the CGM sensor to record of blood sugar levels transmitted to a smartphone app.

Globally, millions of people living with diabetes now use CGM devices. Although these devices have received wide acceptance in the diabetes care community there is growing concern about their side effects. In recent times there have been documented reports of skin infections linked with the Dexcom devices, skin bruisings linked with the FreeStyle Liber products, and the emergence of skin bumps after removing Dexcom devices. Beyond the scope of simply reporting these side effects, many scientific studies have been conducted to understand the extent of inconvenience these devices present in different patient groups.

One such study was conducted in 2007 by researchers from the Faculty of Medicine and Dentistry at two Universities from the Slovak Republic and the Czech Republic. Using a participant pool of 22 healthy volunteers using CGM sensors subcutaneously inserted in the gluteal and lumber region for 9 days the researchers observed the incidence of CGM side effects as local reactions and general disturbances.

During 184 sensor days, side effects reported were largely minor local adverse events including itching, pain, redness, burning, hypersensitivity, and subcutaneous hemorrhage. Although side effects like these are not commonly reported they still occur at a considerable rate in the general population.

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How Do CGM Devices Cause These Side Effects?

Side effects linked to CGM devices are largely of two types: the first type disrupts the skin integrity, while the second adversely disrupts the psychological health of users and/or caregivers.

In both cases, side effects are a big concern for people who utilize CGM devices for diabetes care. Although there are many brands of CGMs on the market today, most float the same design. CGMs have a small filament or cannula designed to be inserted subcutaneously and fastened tight to the skin with an adhesive patch.

Adhesive on these devices vary in size depending on the overall design of the CGM. For instance, adhesives on tube infusion sets have a small surface area, while those on pumps and CGMs are larger.

Depending on the monitoring period, adhesives are worn on the skin for an average of 7 – 14 days before replacement. In many cases, the onset of skin-related side effects is linked to the cannula insertion and the timeframe of adhesive use on the skin. The material of the adhesive determines breathability and the rate of moisture trapping between the sensor and the skin. These metrics appear to have significant effects on the risk of dermatological complications associated with CGMs.

It appears there is a link between medical history and the risk of developing CGM side effects. Individuals with a clinical history of atopic disease showed a higher risk of developing skin reactions to CGM adhesives.

Patients who had never used a CGM or insulin pump before were also likely to experience minor side effects. In many cases, prolonged periods of intense physical activity and sweating have been reported to excavate cases of subcutaneous hemorrhage.

Side effects are also likely to be reported in specific populations. A multicenter randomized controlled trial conducted in 2017 reported that 48% of pregnant women and 44% of women planning pregnancy experienced CGM-related skin reactions. About 31% of the affected population reported erythema; 11% reported chronic dry skin; and 7% reported hyperpigmentation at the site of CGM adhesion.

This trend has also been reported in pediatric populations. A study conducted in Denmark using a participant pool of 144 children reported how 80% of the study population experienced skin issues including pruritus (70%), eczema (46%) and wounds (33%).

Across the popular brands of CGM sensors available in the market today there have been reports of side effects that appear to be brand-specific.

For instance, post-marketing study data have reported more dermatological complications with the Dexcom G5 sensor compared to the FreeStyle Libre.

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Notable Side Effects to Watch Out For

  1. Hypersensitivity

Hypersensitivity reactions are the most reported side effects of CGMs. The result of a 2017 trial reported serious adverse effects associated with the FreeStyle Libre devices. This study informed Abbott’s decision to improve Libre’s adhesive material. Hypersensitivity reactions like these can be type 1, type 2, type 3, or type 4.

Type 1 hypersensitivity reactions are immunoglobulin E (IgE) mediated and are commonly presented as atopic-type skin reactions. These reactions occur within minutes, causing redness and irritation.

Type 2 and type 3 hypersensitivity reactions are not commonly reported.

Type 4 reaction reactions are delayed responses and are the most commonly reported type of hypersensitivity reactions. Type 4 reactions take a longer period of exposure to induce and may be caused by chemicals in the adhesive patches.

  1. Irritant Contact Dermatitis

Also known as allergic contact dermatitis, this side effect is present as a nonimmune inflammatory reaction induced by chemical or physical irritations through an open wound on the skin.

Cannula entry or prolonged use of adhesives may damage the skin’s top layer, increasing the risk of antigenic exposure and a resultant allergic reaction. Chemicals used in the adhesive patches of CGMs have been linked to this side effect. CGM patches made from acrylate monomers have been reported to cause irritant contact dermatitis.

In a 2017 study, a group of researchers in Belgium presented evidence that implicates isobornyl acetate as the relevant culprit allergen in allergic contact dermatitis reactions reported by diabetic patients using the FreeStyle Libre CGM.

  1. Scarring

CGM-related scarring reported so far manifests as small pigmented lesions made entirely of fibrous tissues. Scarring has been reported in both the adult and pediatric populations using CGM devices. The effects of scarring on the accuracy of CGM devices, or the effectiveness of insulin (for CGMs with insulin pumps) remain unclear. However, scarring may disrupt the insertion processes for CGM sensors and cannulas, presenting an area of skin that is not aesthetically pleasing. Patients should avoid scarring sites while selecting new insertion sites.

  1. Lipodystrophy(LH) and Lipoatrophy

Prolonged use of CGM adhesives has been linked to localized loss of subcutaneous adipose tissues (lipoatrophy) and abnormal growth of subcutaneous adipose tissues. Lipoarthrophy is induced by adverse immunological reactions to the biological interaction of insulin with the body. It is more common in CGM designed with an insulin pump. In recent years the development of highly purified insulins has significantly reduced the incidence of CGM-linked LH in diabetes patients. Rotating sites of cannular insertion and sensor attachment also play a crucial role in preventing LH.

  1. Psychological Adverse Reactions

Recently, studies examining the impacts of CGM devices on the quality of life of patients and caregivers have unveiled an interesting finding: beyond the physical side effects reported in cohort studies, CGM devices also seem to present some psychological and behavioral changes.

In 2014, researchers compared sleep quality and sleep-wake patterns in parents of children managing diabetes with a CGM system. Using a participant pool of 13 parents the study demonstrated how CGMS negatively affects parental sleep continuity. Six of the thirteen parents reported severe sleep problems with a considerable number of nighttime awakenings after initiating CGM in their child.

Patients have reported quite a handful of psychological side effects including feeling overwhelmed by the volume of data generated by CGMs, feeling anxious as a result of greater awareness of their glucose levels, and feeling stigmatized when wearing a sensor. There have been other reports of perceived hassles and problems related to nuisance alarms and anxiety in caregivers.

Preventing CGM Side Effects

In many cases, side effects linked with CGMs are due to improper handling of the devices. Understanding the hacks in sensor preparations and installation can help reduce the risk of these side effects.

Here are a few hacks to adopt:

  1. Carefully Consider Device Placement Locations

Device placement has a significant impact on the risk of CGM-linked side effects. The most common areas where patients install their CGM sensors include the abdomen, upper buttock, upper hip, upper thigh, upper arm, and forearm. Click here to read about alternative sensor sites. Although most of these locations are approved by manufacturers the multiple options available may confuse patients on the best location to select. Regardless of the CGM sensor, the best location is where there is a sufficient deposit of subcutaneous tissue. Sensor placement in this region reduces the level of discomfort experienced by patients during cannula insertion, or sensor removal.

In addition, skin should be inspected for color, texture, and previous scarring to determine the appropriateness for sensor placement. Identifying multiple sites for sensor placement based on subcutaneous tissue volume helps patients easily rotate sites and maximize the time needed for skin to heal.

  1. Pre-attachment Skin Care Options

Before sensor placement, a series of skin prophylaxis care may help reduce the risk of hypersensitivity reactions. Barrier agents for CGMs have been developed for this purpose. Thorough cleaning (especially on oily skin types), gentle exfoliation, and the use of water-based moisturizers may be useful. Liquid barriers may protect the skin patch from irritant chemical components of the sensor adhesives. Adhesive bandages developed with skin-friendly adhesives provide a more efficient solution to holding sensors firm and reducing the risk of hypersensitivity reactions. In patients with a history of dermal irritation, over-the-counter topical antihistamines may be considered effective prophylactic agents.

  1. Consider Using Adhesives Patches and Tackifiers

It is important to enhance adhesion throughout the sensor’s lifecycle. Beyond merely preventing premature peeling, modern CGM sensor adhesive patches and tackifiers are designed to reduce the burden of dermatological irritation. Most are made from breathable materials, making it possible to avoid the risk of skin pore clogging and irritation caused by increased perspiration.

They are particularly important in children and adults with high activity levels. Adhesive patches are also made from hypoallergenic materials. These materials are largely safe on different skin types, reducing the risk of hypersensitivity reactions.

  1. Employ Safe Removal Techniques and Agents

Adopting safe removal techniques during sensor removal protects the skin from cuts and microdamages. In turn, this reduces the risk of contact dermatitis and mechanical damage to the CGM. Adhesive tapes should be slowly removed to preserve the skin’s surface integrity. There are also many removal aids available on the market today. Post-removal cleaning also helps remove oil residue on the skin.

Final Note

Continuous glucose monitoring (CGM) devices are medical devices and should be treated as such. The side effects related to these devices can occur in any patient. Generally, these products are considered safe. However, a small percentage of the population may experience serious side effects. Getting familiar with post-marketing reviews and publications on these devices is a good tactic to stay safe and avoid the risk of side effects.

Below we have added some quick FAQs to assist you further. 

The best locations for sensor placement are areas with a relatively large volume of subcutaneous tissue. You can consult the sensor manual for further details on site selection. For children, you should select a relatively flat surface, not likely to crease during movement.

You can consider over-the-counter topical antihistamines. You can also consider using skin-friendly adhesive patches.

Gently clean the skin and inspect the extent of the injury. If the skin is intact and not bothersome, apply moisturizing lotion to soothe and protect the skin.

In severe allergic reactions, you should consult a dermatologist for patch testing and possible clinical intervention

*Disclaimer: The information within this blog is for informational and educational purposes only.

Article written by Adil Maqbool, MD

Dr. Adil has been a speaker at various medical conferences and health awareness campaigns, where he shared his research and findings, and advocated for accurate medical knowledge. He has been featured in publications such as Cardiology & Vascular Research, The Journal of Physical Fitness and Sports Medicine, and The Lancet.

Last medically reviewed on March 24, 2024

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