Overview

You can make a cheap, stable medication refrigerator by plugging a chest freezer into a thermostat-controller, which will power the chest freezer on and off to maintain an appropriate temperature range.

It will hold a much narrower temperature range than most home refrigerators. This is most important if you have medications with a narrow acceptable temp range, like biologics.

You can do this for about $50 if you can find a free, working chest freezer. I spent about $300 on my setup.

Why? Medications and refrigeration

Some medications need to be kept within certain refrigerated temperature ranges. The range is usually 36-46F.

Unfortunately, home refrigerators:

  • Swing widely in temperature
  • Have warm and cold zones. Ever opened your fridge to frozen spinach on a shelf? Had your milk go bad fairly quickly because you kept it in the door?
  • Should be kept colder (for food safety/longevity) than is wise for your medication temps
  • Are subject to many openings/closings a day, which can raise the temperature considerably

Okay, so what about medical-grade, pharmacy style fridges? Well, anything that promises tight ranges and real stability is like $10,000 USD.

You should monitor fridge temperature

First consider this step, even if you’re storing your meds in your normal fridge. It’s pretty cheap to pick up a battery-powered, remote-read thermometer with configurable hot/cold alarms and a 24h hottest/coldest temperature memory.

This lets you at least find a spot in the fridge where you can be certain your meds won’t risk freezing or repeatedly go above range.

You could also upgrade to a sensor that will record data and and send it to your phone via BlueTooth. Upgrade that with a wifi gateway, and you can see the temperature of your medication at any time. With graphs! See Materials section for details.

One warning: your newfound data can be very stressful if your refrigerator has really big temperature swings. Sometimes I’ve almost wished for the simpler days of ignorance, but hey, the medications were still getting just as far out of range, I just didn’t know about it.

Or, maybe you’re lucky and your home fridge holds great temperatures! You can then skip the rest of this page. Maybe get a power station and/or keep some extra gel packs frozen and refrigerated so you can hold ideal temperatures in case of a power outage. For everyone else, read on.

Help from an unexpected source: the “keezer”

You can make a relatively inexpensive, highly temperature-stable refrigerator with a tiny bit of tinkering. To learn how to do this, I turned to a group of people who have very similar needs for a stable, consistent temperature in a very small window: homebrewers.

Enter the thing called a keezer, like a kegerator but a “keg-freezer”—a name I find so aesthetically displeasing I generally refuse to use it (but you need to know it as a search term, so here you go). I refer to it as the “meds fridge” instead. The best part is that our meds fridge can be way simpler: no CO2, no ‘collar’ to allow for taps and lines, no kegs.

Materials

Here’s what you’ll need. I will add (non-affiliate) links to what I use, but plenty of others will work. I’ll discuss what each piece needs to achieve for you.

Optional upgrades (but recommended)

The wifi version of the Inkbird is not much more expensive than the non-wifi version and comes with an app that gives you all the benefits of a separate sensor + wifi gateway system, so I recommend doing the wifi-thermostat route if you can. (On the other hand, I suppose there’s a security factor: wifi-connected devices are often not all that secure, and a wifi-enabled thermostat affects actual fridge temp, while a wifi-enabled sensor only affects monitoring.)

Even more optional upgrade

  • A big power station battery, if you live in an area with power outages
  • Solar panels for it, if you expect long outages

Notes on specs

Chest freezer: you can often find working ones for free or cheap on Craigslist or FB Marketplace. In the US, BestBuy sells small ones pretty cheap, especially around sale time. Newer may be better in terms of efficiency and how much power it uses.

Thermostat: you need a thermometer that also controls an outlet. It should allow you to set a target temperature and a “turn on” cooling differential. For example, mine is set to a target temp of 44°F, it starts cooling with a 1-degree differential (i.e. the freezer kicks on at 45°F), and it stops cooling when it returns to the target temperature. Because of how cooling works, the temperature will keep coasting downward for awhile after cooling kicks off. Some thermostats have more features.

Remote temp sensor + wifi gateway: a continuous record of temperatures is an enormous aid for high-stakes, expensive medications like biologics. Especially if you’re not home.

Power station: a nice backup if you have power outages. Even if you keep ice packs around or it’s frozen outside, it’s hard to keep things at juuuust the right temperature using only ice. The power station rabbit hole goes deep but they’re pretty cool devices.

How to build

  1. Plug thermostat into the wall. Plug chest freezer into the thermostat.
  2. Set up your thermostat. Here’s the page I used for my Inkbird, but you can follow the instructions on whatever thermostat you end up with. I typically do a set temperature of 40°F with a cooling differential of 1°F. That means it’ll start cooling at 41°F and stop actively cooling when it comes back down to 40°F, with a couple degrees of coasting on either side.
  3. Situate your probe and let the cycles even out. Hard-won lesson: any time you change something, the fridge may do some major temperature swings as it readjusts. Plan to be around to babysit if you’ve changed a setting or added/removed a decent amount of thermal mass.
  4. Optional: set up additional remote temperature monitoring, if you didnt get a wifi-enabled thermostat. Make sure you put the sensor under similar conditions to your meds and the thermostat probe.
  5. Adjust thermal mass for stability. Put some cardboard next to the cooling coils, and put some jugs of water in there to take up extra air space. A few of the gel packs your medication probably ships in are also a good choice.
  6. Optional: plug the chest freezer into a portable power station battery (aka “solar generator”). Get a sense of how long it would last on a full charge.
  7. Put your meds in your new meds fridge!
  8. Profit Enjoy your newfound medication temperature stability.