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Use thicker sheets. Buy a down comforter. Pile up your pillows. Get a hot water bottle. Use an electric blanket.
Cotton sheets are great year round. But if you find that you need a little more heat during the winter, consider getting flannel sheets. They are soft, warm, and will keep you nice and insulated. Other materials that hold heat well are wool, fleece, and silk.  You can find a wide variety of sheets at home goods stores, department stores, and online. One benefit to buying sheets in person is that many stores have samples of the fabrics for you to feel. This will help you to get an idea of what will work best for you. Down comforters are typically much more expensive than other blankets. However, you might find this to be an investment worth making. There are several different weights of down comforters. The heavier ones are meant to keep you warm on cold nights. If you end up liking the down, you can find a lighter version for summer. If you are allergic to goose down, there are synthetic options available. Pillow can also insulate you and keep you warm. Use several pillows to pile around you to make sort of a fort or igloo. This barrier will help keep your body heat in.  You’ll need at least 3-4 extra pillows to make this effective. Make sure to give yourself enough space to move around as you need to in your sleep. Sometimes the most traditional methods still prove to be some of the most effective. Hot water bottles might be considered old-fashioned, but they get the job done. Purchase a silicone hot water bottle at your local drugstore or online.  Each night before bed, fill it with water that you have heated on the stove. Use a wool or flannel sleeve to cover your bottle. That will make it more comfortable to have in bed with you. Pop it under the covers with you and enjoy the warmth! Electric blankets are a great way to add some extra heat to your bed. These are full size blankets that you use in addition to your sheets and comforter. Choose one with an adjustable heat setting so that you can set the temperature to your liking.  Try a heated mattress pad. These are similar to an electric blanket, but go underneath your sheets. Make sure to carefully read the directions and follow the safety tips. Turn the blanket off before falling asleep.