How to Keep a Hot Water Bottle Hot

Fill your bottle with very hot, but not boiling, water.

Boil a kettle of water and let it cool until it’s no longer scalding. Then, fill your hot water bottle up 75% of the way and squeeze out the excess air before screwing the cap on. Using very hot water is the best way to ensure your bottle stays hot for as long as possible. However, never fill a hot water bottle with boiling water. Boiling water can damage your bottle and cause serious burns if it comes into contact with your skin. As a good rule of thumb, wait 15-20 minutes after boiling the water to let it cool down.

Wrap the bottle with a towel or cover before using it.

A towel or cover will help trap in heat. It's also necessary to protect you from burns. Make sure the bottle is completely covered. You can buy special covers designed specifically for hot water bottles, or you can just use a towel. Either one works!

Refill your hot water bottle if it cools off.

Avoid reheating a hot water bottle. If your bottle feels like it’s getting cold, dump out the leftover water and refill it with a new batch of hot water. Never reheat your hot water bottle in the microwave or oven unless the instructions that came with it specifically say that it's safe to reheat.

Upgrade to a bigger hot water bottle for longer-lasting heat.

Small hot water bottles lose heat more quickly than large ones. If you find that your hot water bottle isn't staying warm as long as you'd like it to, consider buying a bigger one. A bigger hot water bottle will stay warm for longer.

Opt for a thermoplastic hot water bottle.

Thermoplastic bottles trap in more heat than bottles made out of rubber. Plus, thermoplastic bottles are usually opaque, so you can easily see the water level when you're filling them. The one downside to thermoplastic hot water bottles is that they're more prone to leaking than rubber ones. That means you might need to replace your bottle more often, but it might be worth it if you really want a bottle that stays hot for longer.

Consider water-free alternatives to hot water bottles.

Water-free alternatives are easier to keep hot. Some microwavable hot water bottles don’t actually need water—you just heat the pouch up in the microwave and you're good to go. There are also electric hot water bottles, which don't use any water either, that plug into the wall and stay hot constantly. You may find that a water-free alternative is easier to manage and keep warm.

Don't place a hot water bottle on your body for more than 15 minutes.

Hot water bottles can cause serious burns if they're used for too long. Experts don't recommend using hot water bottles directly on your body. Instead, they suggest placing your hot water bottle under the covers in your bed to warm it and then removing it before you get in. If you do place a hot water bottle directly on your body, make sure it's not for longer than 15 minutes. You can start to develop serious burns after 15 minutes of direct contact with a hot water bottle. You might not be able to feel yourself getting burned until it's too late. Avoid sitting or rolling on your hot water bottle—this can cause your bottle to burst, which can lead to burns.