Your body temperature naturally drops at night as part of your sleep cycle, but a sudden or noticeable change in how cold you feel can signal something beyond normal biology. The most common culprits range from hormonal shifts and low iron levels to thyroid problems, blood sugar dips, and simple environmental factors like bedding or room temperature.
Your Body Is Supposed to Cool Down at Night
Core body temperature begins declining before you even fall asleep, and it continues dropping until it hits its lowest point sometime during the night. You typically wake up a few hours after that low point, as your temperature starts climbing again. This natural dip is actually a feature, not a bug. The rate of that presleep temperature decline is directly tied to how quickly you fall asleep and how well you sleep overall.
So some degree of feeling cooler at night is completely normal. The question is whether something has changed. If you’ve always slept comfortably and now find yourself shivering or waking up cold, that shift is worth paying attention to.
Hormonal Changes and Your Internal Thermostat
Estrogen plays a direct role in how your body conserves heat. It acts on a circuit in the hypothalamus, the brain region that functions as your internal thermostat, to suppress heat loss through the skin. When estrogen levels drop or fluctuate, that heat-conservation system can malfunction.
This is most obvious during perimenopause, when changing estrogen levels trigger vasomotor symptoms like hot flashes and night sweats. What many people don’t realize is that a hot flash is often followed by a dip in core temperature as the body overcorrects after flushing heat to the skin. The result can be a cycle of sweating followed by chills. Interestingly, research suggests it’s estrogen withdrawal, meaning a drop from a previous level, rather than simply having low estrogen that triggers these episodes. People with chronically low estrogen who never had higher levels don’t experience the same symptoms.
Hormonal shifts aren’t limited to menopause. Monthly cycle fluctuations, postpartum changes, and certain medications that affect hormone levels can all disrupt nighttime temperature regulation in similar ways.
Low Thyroid Function
Hypothyroidism is one of the most common medical reasons for increased cold sensitivity, and it tends to be more noticeable at night when your body is already cooling down and there’s no physical activity generating extra warmth.
Thyroid hormones regulate your basal metabolic rate, which is the baseline amount of energy your body burns at rest. When thyroid levels are low, that metabolic rate drops, and so does your heat production. The mechanism goes deeper than just “slower metabolism,” though. Thyroid hormones stimulate processes in your muscles that consume energy and release heat as a byproduct. They also play a key role in activating brown fat, a specialized tissue whose primary job is generating warmth. On top of that, thyroid hormones make your tissues more responsive to the stress hormones that drive cold adaptation. Without adequate thyroid function, your body simply can’t mount a proper defense against cold.
Research confirms that cold-induced heat generation is measurably reduced in people with hypothyroidism and returns to normal once thyroid levels are restored with treatment.
Iron Deficiency and Anemia
Iron deficiency anemia consistently shows up in research as a cause of poor temperature regulation. The connection works through two pathways. First, iron deficiency impairs thyroid function, which reduces heat production through the mechanisms described above. Second, anemia means fewer red blood cells carrying oxygen to your tissues. Your body then faces a conflict: it needs to keep blood flowing to vital organs for oxygen delivery, but it also needs to restrict blood flow to the skin to prevent heat loss. These competing demands make it harder to stay warm, especially at night when circulation naturally slows.
If your sudden nighttime coldness comes alongside fatigue, pale skin, or shortness of breath during mild activity, iron levels are worth checking.
Blood Sugar Drops During Sleep
Low blood sugar, or hypoglycemia, can cause your body to lose heat in two ways: it triggers sweating and widens blood vessels near the skin, both of which dump heat into the surrounding air. If blood sugar drops far enough, typically between 30 and 45 mg/dL, shivering actually shuts down. Your body prioritizes glucose for brain function and breathing over generating warmth through muscle contractions. Shivering only resumes once blood sugar levels come back up.
Nocturnal hypoglycemia is most relevant for people with diabetes, particularly those on insulin or certain medications. But it can also occur in people who skip dinner, eat very low-carb meals in the evening, or drink alcohol before bed, which suppresses the liver’s ability to release stored glucose overnight.
Nerve Damage and Circulation Problems
If the cold feeling is concentrated in your hands or feet, peripheral neuropathy could be involved. Nerve damage alters how your body senses and responds to temperature. Specifically, injury to sensory nerves can change how cold-detecting channels in the skin function, making normal room temperatures feel uncomfortably cold. This cold hypersensitivity, where cool conditions that previously felt fine now provoke discomfort, is a hallmark of certain types of neuropathy.
Poor circulation compounds the problem. When blood vessels in the extremities constrict or don’t function well, less warm blood reaches your fingers and toes. At night, when you’re lying still and not generating heat through movement, this becomes more pronounced. Conditions like Raynaud’s phenomenon, diabetes-related vascular damage, and peripheral artery disease all reduce blood flow to the extremities and can make nights feel especially cold.
Calorie Intake and Meal Timing
What and when you eat before bed affects how much heat your body produces during sleep. After eating, your body generates extra heat through the process of digesting and metabolizing food. Larger meals produce significantly more of this post-meal heat than smaller ones. However, falling asleep triggers a sharp drop in that heat production, along with a decline in core body temperature.
If you’ve recently started eating less, dieting, or shifting to earlier dinners, your body may be producing less heat during the night than it used to. Very low-calorie diets reduce basal metabolic rate over time, meaning your body generates less warmth around the clock, with the effect most noticeable when you’re lying still in a cool bedroom.
Your Room and Bedding Setup
The recommended bedroom temperature for sleep is 60 to 67°F (15 to 19°C). Below 60°F is too cold for most people, and above 70°F is too warm. If your thermostat, a drafty window, or a change in season has pushed your bedroom outside that range, that alone could explain the sudden chill.
Bedding materials matter more than most people think. Cotton percale and linen are the most breathable fabrics, which is great for hot sleepers but can leave cold sleepers feeling exposed. If you’ve recently switched sheets or blankets, particularly to a lighter or more breathable material, you may have inadvertently reduced your nighttime insulation. Synthetic fabrics marketed as “cooling” often work by wicking moisture away from the body, which accelerates heat loss. For someone already feeling cold, layering with warmer, less breathable materials or adding a blanket may be a simple fix.
Signs That Something More Is Going On
Occasional nighttime chilliness, especially during seasonal transitions or after a light dinner, is usually nothing to worry about. But persistent or worsening cold sensitivity paired with other symptoms points to an underlying condition worth investigating. Fatigue alongside coldness suggests thyroid dysfunction or anemia. Tingling or numbness in the hands and feet points toward neuropathy or circulation issues. Unexplained weight changes in either direction can indicate thyroid problems, diabetes, or metabolic shifts. Night sweats alternating with chills are characteristic of hormonal changes, infections, or occasionally more serious conditions.
A basic blood panel checking thyroid function, iron levels, blood sugar, and a complete blood count can rule out or confirm the most common medical causes. If your nighttime coldness started suddenly and you can’t trace it to an obvious environmental change, those tests are a reasonable starting point.