Hot tubs, saunas, and heat with pumps and CGMs

Hot tubs on vacation, saunas at the gym, a heatwave at home: heat shows up everywhere, and it interacts with basically every piece of T1D equipment you own. None of it is a reason to skip the soak. All of it is worth ten minutes of understanding.

What heat does to insulin

Insulin is a protein, and heat denatures proteins. In-use insulin is comfortable at room temperature, but the failure zone starts far lower than people assume: a parked car in summer, a beach bag in the sun, a pump pressed against you in a sauna. The nasty part is that heat-damaged insulin usually looks identical to healthy insulin. Sometimes you get clumping or discoloration as a clue; usually you get nothing except numbers that stop responding and a mystery high that correction after correction won't fix.

So the rule of thumb: if your insulin spent time somewhere you wouldn't leave a chocolate bar and your glucose has gone stubborn, swap the cartridge or pen before you chase highs all day.

The hot tub and sauna protocol

1. Disconnect the pump

   Most tubing pumps and even water-resistant pumps aren't rated for prolonged 100-plus-degree water, and the insulin inside definitely isn't. Disconnect, cap the site, and leave the pump in a cool dry spot outside the hot room, not on the tub ledge. Patch pod users can't disconnect, which means the pod and its insulin take the heat with you; shorter sessions and a plan for "what if this pod's insulin cooked" are the trade.

2. Mind the clock

   A disconnect means no basal delivery. Most guidance treats up to about an hour as manageable territory, but the right window for you is a care team question. Set a timer, because hot tub time moves differently.

3. Watch for the heat drop

   Warm water dilates blood vessels and speeds up absorption of any insulin already on board, and heat itself lowers glucose for many people. A soak shortly after a bolus can drop you faster than the same bolus on a normal evening. Check before you get in, keep fast sugar within arm's reach, and get out and check if you feel off. Heat symptoms and low symptoms overlap: dizzy, shaky, sweaty covers both.

4. Reconnect and verify

   When you're done: dry the site, reconnect, and confirm delivery resumed. Check glucose within the following hour to see where the session actually left you.

Keeping things stuck

Heat, sweat, and soaking are the adhesive triple threat, and summer is when sensors start peeling at the edges. The community's proven stack, in order of effort: dry the site thoroughly before and after water. Add an overpatch or adhesive sleeve over the sensor before swimming or soaking rather than after edges lift. For chronic sweat, the pro move is a non-deodorant antiperspirant applied to the site area 10 to 15 minutes before insertion, then cleaned off and fully dried; it keeps the skin underneath drier for days. Barrier wipes and skin preps add another level if you need it.

Travel and heatwave notes

For hot destinations and heatwaves, the enemy is cumulative exposure. Insulated cases with a cool buffer (never direct ice contact, which can freeze insulin and kill it just as dead) handle transit days. At the destination: insulin stays in the room away from windows, never in a parked car, and backup supplies split between bags. Devices mostly ride out heat fine as long as they're on your body or in shade; it's the bag left in the sun that writes the sad stories.