Preparing for a colonoscopy often leads to an intense feeling of coldness. Many people report shivering and struggling to stay warm. This side effect is a direct result of significant changes in the body’s temperature regulation system. Understanding the physiological mechanisms behind this chill helps manage the preparation more comfortably.
Rapid Fluid Loss and Heat Dynamics
The prep solution involves drinking several liters of fluid over a short period. This massive influx of liquid, often room temperature or chilled, initially lowers the core body temperature.
The rapid transit and expulsion of this liquid carries heat away from the body. Frequent trips to the bathroom expose the body to cooler air and interrupt the body’s ability to maintain a stable thermal environment. Expelling large amounts of stool and water is physically demanding, but it does not generate enough sustained internal heat to counteract the loss.
Metabolic Slowdown from Calorie Restriction
Dietary restrictions before a colonoscopy, such as a clear liquid diet or fasting, contribute to the cold sensation by slowing metabolism. Digestion of solid food generates heat (diet-induced thermogenesis). When solid food intake ceases, this heat-generating process shuts down.
Recognizing the reduction in caloric intake, the body prioritizes energy conservation. It lowers the basal metabolic rate (the energy expended while at rest). Less energy is burned, producing less heat. This conservation strategy is protective, but it leaves the individual feeling colder.
How Dehydration Triggers Vasoconstriction
The cumulative effect of the preparation leads to mild dehydration, triggering the body’s protective response: vasoconstriction. Rapid fluid loss decreases blood plasma volume, meaning less fluid is available to circulate and distribute heat.
In response to this reduced circulatory volume, the body initiates peripheral vasoconstriction, narrowing small blood vessels near the skin and in the extremities. This narrowing restricts blood flow to the periphery. This action shunts warm blood inward, concentrating it around vital organs (heart, lungs, brain) to maintain core temperature.
While effective at protecting vital organs, this maneuver reduces the temperature of the skin and extremities. The lack of warm blood circulation in the periphery is the direct cause of the intense chill felt during the prep period.
Practical Steps for Staying Warm
Managing the intense cold involves proactive steps focused on external warmth and internal replenishment.
- Employ strategic layering of clothing, using thermal wear, thick socks, and a hat, since a significant amount of body heat is lost through the head. Multiple thin layers trap heat more effectively than a single heavy layer.
- Create a warm environment by setting the thermostat higher than normal and keeping a heating pad or electric blanket nearby. These external sources provide warmth without requiring the body to generate it internally, easing the strain on the metabolic system.
- Consume approved warm clear liquids, such as clear broth, weak tea, or slightly heated clear apple juice. The warmth transfers directly to the core, offering temporary relief, but always check the specific list provided by the healthcare provider to confirm which liquids are permissible.
- Monitor for signs of worsening dehydration. If shivering becomes uncontrollable or if symptoms like dizziness or confusion appear, contact a healthcare provider immediately.