Warmhold Sherpa Heated Blanket in Dark Gray draped over an armchair

Is it safe to sleep with a heated blanket on?

This is the question we get most, and the honest answer is: it depends on the blanket and on how you use it. The heated blankets that earned the category its reputation were old ones with no timer, no temperature sensing, and wires that failed after a decade of folding. A blanket made in the last few years is a different object.

What a modern blanket does on its own

It switches itself off. Ours has six timer settings, and if you don't pick one it turns off after 10 hours regardless.
It watches its own temperature. A self-regulating PTC heating wire draws less current as it gets warmer, and an NTC sensor reads the temperature continuously. If anything runs hotter than it should, overheat protection cuts the power.
It warms gently. The highest setting is designed to be comfortable against skin, not to heat a room. If you want hotter than that, a heated blanket isn't the right tool.

What you do

Keep it flat. Don't fold it, bunch it, or sit on the controller while it's on. Heat builds up in a fold.
One source of heat. Don't use it with a hot water bottle or heating pad, and don't pile another heavy blanket on top of it.
Don't tuck it in. Tucking traps heat and strains the wire at the edges.
Use the timer. Warm up under it, then let it switch off once you're asleep. A warm body under a good blanket stays warm.
Check it now and then. Scorch marks, a bunched wire you can feel, or a controller that gets hot are reasons to stop using it.

Who shouldn't use one

Infants, young children and pets, because they can't tell you if it's too warm or work the controls. Anyone with reduced sensation or who can't operate the controller themselves. If you have a pacemaker, diabetes or poor circulation, or you're pregnant, talk to your doctor first; they'll usually say it's fine on a low setting, but it's their call.