How to Keep CGM Sensors Warm in Cold Weather (and Prevent Winter Sensor Failures)
Cold weather and CGM sensors do not get along. If you’ve got a child or teenager living with Type 1 Diabetes, winter can bring a whole new set of frustrations: sensor errors, signal loss, “sensor unavailable” messages, or readings that suddenly make no sense.
You’re not imagining it. Cold really can interfere with sensor performance. The good news? There are practical, everyday ways to keep sensors warm and working, even during icy school mornings, winter sports, and long outdoor days.
Why Cold Weather Affects Sensors
CGM sensors rely on:
Enzyme reactions under the skin
Adequate blood flow
Stable temperatures
Dexcom themselves state that their sensors operate best within a temperature range of 10 degrees C to 42 degrees C (50 degrees F to 107.6 degrees F). Freestyle Libre has a similar range of 10 degrees C to 45 degrees C (50 degrees F to 113 degrees F). Exposure to temperatures outside this range, particularly extreme cold or extreme heat can affect sensor accuracy and may lead to temporary signal loss or complete sensor failure.
Cold causes vasoconstriction (reduced blood flow), which can lead to:
Inaccurate or delayed readings
Sensor dropouts
“Sensor unavailable” messages
Premature sensor failure
Children and teens are especially vulnerable because they spend more time outdoors, wear thinner clothing for PE, and are less likely to notice when a sensor is getting cold.
Practical Ways to Keep Sensors Warm
1. Layer Clothing Over the Sensor
One of the simplest and most effective strategies.
What helps:
A snug base layer over the sensor
Thermal vests or long-sleeved undershirts
Avoid leaving sensors exposed under short sleeves in winter
School tip: If PE kits require short sleeves, ask for permissions to wear a thin thermal or compression layer underneath.
2. Use Sensor Covers or Overpatches
Extra adhesive layers don’t just keep sensors stuck on, they also add insulation.
Helpful options include:
Fabric or foam-backed overpatches
Full sensor covers
Compression sleeves for arm sensors
These are particularly useful during outdoor play, sports, or long periods in cold air.
3. Choose Winter Friendly Sensor Placement
Some sensor sites are more exposed to the cold than others.
Often better winter locations:
Upper arm under long sleeves
Abdomen under multiple layers
Upper thigh under trousers
More vulnerable areas:
Arms left uncovered
Sites exposed to wind chill
Rotating sensor placement with the seasons can noticeably improve performance.
4. Keep the Whole Body Warm
This is a big one that’s easy to overlook.
When the body temperature drops, blood flow decreases, including to the sensor site.
Focus on:
Warm coats, hats, gloves, and scarves
Insulated footwear
Keeping the core warm
A warmer body often means more reliable sensor readings.
5. Be Mindful During Winter Sports and Outdoor Play
Skiing, football, playground time, winter walks, or standing still in cold weather can chill sensors quickly.
What can help:
Compression sleeves over arm sensors
Extra layers added just for outdoor time
Short warm-up breaks indoors where possible
If readings suddenly drop or disappear during cold exposure, warming the area often restores them.
6. Warm the Sensor Area Gently if It Starts to Fail
If a sensor begins acting erratically due to cold:
Move indoors
Add layers
Use body heat (placing a warm hand over clothing)
Avoid external heat sources directly on the sensor- slow, natural warming is safest.
7. Protect Sensors During the First 24 Hours
New sensors can be especially sensitive to temperature changes.
In cold weather:
Avoid inserting right before long outdoor exposure
Insert in the evening so body warmth supports warm-up
Keep the site well covered during the first day
This can reduce early sensor failure.
A Reassuring Note for Parents and Teens
Cold related sensor problems are not a failure in diabetes management. Even manufacturers acknowledge that sensors have optimal operating temperature ranges, and going outside those limits can affect accuracy and performance.
Always:
Trust symptoms over sensor numbers in extreme cold
Use finger prick checks if readings don’t match how someone feels
Encourage children and teens to speak up when something doesn’t seem right
The Bottom Line
CGM technology is life changing, but it still has limits. Dexcom and Freestyle Libre sensors are designed to work best between 10 degrees C and 42/45 degrees C, and winter conditions can push them outside that comfort zone.
With thoughtful layering, smart placement, and a few winter adjustments, many cold weather sensor failures can be reduced or avoided.
