Shivering is your body’s automatic heating system. When your core temperature drops, a region of the brain called the hypothalamus triggers rapid, involuntary muscle contractions to generate warmth. But cold isn’t the only cause. Fever, anxiety, low blood sugar, and even surgery can set off the same reflex. The fix depends on what’s driving it.
Why Your Body Shivers
The hypothalamus constantly monitors your blood temperature. When it detects a drop below your normal set point, it activates a cascade of responses: blood vessels near the skin constrict to keep warm blood closer to your organs, your adrenal glands release stress hormones to boost your metabolic rate, and your skeletal muscles start contracting rapidly. That rapid contraction is the shiver itself, and it’s surprisingly effective at producing heat quickly. Goosebumps are part of the same reflex, an evolutionary leftover from when body hair was thick enough to trap a layer of warm air against the skin.
During a fever, the same mechanism kicks in for a different reason. An infection resets your hypothalamus to a higher target temperature. Your brain now “thinks” 101°F or 102°F is normal, so your actual body temperature feels too cold by comparison. That mismatch triggers shivering even though you’re already running hot. This is why you can feel freezing and feverish at the same time.
Stopping Shivers From Cold
The most straightforward shivers come from being cold, and the fix is exactly what you’d expect: get warm. But how you warm up matters. Layering clothes traps body heat more effectively than a single thick garment because the air between layers acts as insulation. If you’re indoors, pile on blankets and focus on covering your torso and head, where heat loss is greatest.
Warm drinks help from the inside out. Hot tea, coffee, or cocoa raises your internal temperature and gives your hypothalamus the signal that warming is underway. Avoid alcohol, which feels warming but actually causes blood vessels near your skin to dilate, pulling heat away from your core and making the problem worse.
If you’re stuck outside or can’t access warm clothing, physical movement is your best tool. Walking briskly, doing jumping jacks, or even clenching and unclenching your fists generates muscle heat through voluntary effort rather than the involuntary kind. Once your core temperature starts rising, your hypothalamus dials back the shiver reflex on its own.
Calming Anxiety-Related Shaking
Anxiety and panic attacks can produce shivering that looks and feels identical to cold shivers, but the trigger is adrenaline rather than temperature. Your nervous system floods your body with stress hormones, your muscles tense up, and the excess energy comes out as trembling or shaking. Adding a blanket won’t help much here because the problem isn’t temperature.
Controlled breathing is the most reliable way to interrupt this cycle. Slow your exhale so it’s longer than your inhale, something like four counts in and six counts out. This activates the branch of your nervous system responsible for calming you down. Within a few minutes, your heart rate drops and the trembling typically follows.
Grounding techniques can also help. Press your feet firmly into the floor and focus on the sensation of weight moving through your legs. This redirects your brain’s attention away from the panic loop and toward physical sensation, which helps release the tension your muscles are holding. Deliberate, effortful movements like squeezing a pillow hard and then releasing it can burn off some of that excess adrenaline and give the shaking somewhere to go.
Shivers During a Fever
Fever-related shivers, sometimes called rigors, are among the most intense. They can involve full-body shaking that feels impossible to control. Your instinct to reach for blankets is actually the right move in the short term. Because your brain has set a new, higher target temperature, warming the skin helps close the gap between where your body is and where your hypothalamus wants it to be. Research shows that skin temperature contributes about 20% to the shivering reflex, so even moderate external warming can make a meaningful difference.
Once your fever breaks and your set point returns to normal, the opposite happens. You’ll suddenly feel too hot, start sweating, and the shivers stop. At that point, you can shed the extra layers. In the meantime, staying hydrated is critical because fever increases fluid loss significantly. Over-the-counter fever reducers work by lowering the hypothalamic set point itself, which addresses the root cause of the shivering rather than just the symptom.
Low Blood Sugar as a Hidden Cause
When blood sugar drops below 70 mg/dL, your body responds with a burst of adrenaline that can cause shaking, sweating, a racing heart, and dizziness. If you haven’t eaten in a while, or if you have diabetes and your levels dipped, this is worth considering. The shaking from low blood sugar feels different from cold shivers. It tends to affect your hands first and comes with hunger, irritability, or mental fogginess.
The fix is fast-acting sugar: a few glucose tablets, half a cup of juice, or a tablespoon of honey. These can bring your levels back up within 15 minutes. If you notice this pattern regularly but don’t have diabetes, eating smaller, more frequent meals with a mix of protein and complex carbohydrates helps prevent the blood sugar swings that trigger it.
Post-Surgery Shivering
Shivering after surgery is extremely common and happens because anesthesia temporarily disrupts your body’s ability to regulate temperature. Your core temperature can drop during a procedure, and once you start waking up, your hypothalamus notices the deficit and fires up the shiver response aggressively. Hospitals typically use forced-air warming blankets (devices that blow heated air through a special cover) to raise skin temperature and suppress the reflex. If you’re recovering from surgery and shivering intensely, this is normal and your care team will have protocols ready. It usually resolves within 30 to 60 minutes with active warming.
When Shivering Signals Something Serious
Most shivering is harmless and stops once the underlying cause is addressed. But certain patterns deserve prompt medical attention. Shivering combined with a stiff neck, confusion, or unusual sluggishness can indicate a serious infection or meningitis. Prolonged rigors lasting hours, especially with a high fever, may point to sepsis. And shivering without an obvious cause, particularly if it’s accompanied by persistent tremors at rest or during intentional movement, could reflect an electrolyte imbalance. Low magnesium, for instance, is linked to tremors, muscle spasms, and neuromuscular irritability, and these symptoms often resolve once levels are corrected.
The Role of Magnesium
Magnesium plays a key role in muscle and nerve function, and deficiency is more common than most people realize. When levels drop too low, muscles become hyperexcitable, which can show up as tremors, twitching, or spasms that mimic shivering. In a review of 60 cases, roughly 23% of people with low magnesium had postural tremors (shaking when holding a position), and nearly half had problems with balance and coordination. Correcting the deficiency, especially through intravenous supplementation in severe cases, led to rapid improvement in many patients, sometimes within hours.
If you experience unexplained trembling along with muscle cramps, fatigue, or an irregular heartbeat, a simple blood test can check your magnesium levels. Dietary sources like nuts, seeds, leafy greens, and whole grains support healthy levels, and oral supplements are widely available for mild deficiencies.