Core temperature bottoms out in the early hours, so you wake cold even in a room that felt fine at midnight.
Layers within reach, seasonal bedding, and socks solve the normal version. The patterns that matter: freezing plus drenched in sweat suggests fever swings; freezing with shaking, sweating, hunger, and palpitations fits low blood sugar, which heavy drinking or exercise without eating can trigger per the NHS; and feeling cold around the clock with fatigue, weight gain, and constipation is the underactive thyroid cluster, which a blood test checks. Drenching sweats, fever, or weight loss join the list of GP reasons.
What to do
Common questions
Why do I wake up freezing at night?
Your body runs cold at 4am by design. Core temperature drops through the night as part of normal sleep physiology, hitting its low point in the early morning, so a duvet that was perfect at midnight leaves you shivering toward dawn, especially in a room that has also cooled. That is the everyday explanation, and the fix is layers you can pull on half-asleep, a warmer duvet for the season, and socks. The patterns that mean more: waking freezing and soaked in sweat is the fever pattern, where your temperature regulation is swinging; waking freezing with shaking, sweating, hunger, and a racing heart fits low blood sugar, whose NHS symptom list includes sweating, shaking, hunger, and heart palpitations, and heavy evening drinking or a lot of exercise without eating can set it up; and feeling cold more than usual all the time, not just at night, with fatigue, weight gain, and constipation, is the underactive thyroid cluster the NHS lists, checked with a simple blood test. New drenching night sweats, fever, or unexplained weight loss alongside the freezing wake-ups deserve a GP visit rather than a thicker blanket.