Winter Work: Why Kidneys Work Harder in the Colder Months
Contributor: Mercedeh Kiaii, MD, FRCPC
Winter places unique demands on our kidneys. It changes how our body balances fluids, blood pressure, and waste. Understanding why kidneys may be under extra strain in the colder months helps us take practical steps to protect them, adjust our habits, and reduce the risk of added stress on the body during winter.
FLUID BALANCE BECOMES MORE COMPLICATED
Many people feel less thirsty in the cold, so they may drink less water. At the same time, the body loses fluids more quickly in dry winter air through breathing and evaporation. The kidneys must work harder to keep fluids and electrolytes balanced, often producing more concentrated urine. This can increase the risk of kidney stones and make it harder for the kidneys to maintain equilibrium.
SALT-HEAVY COMFORT FOODS
Winter diets often lean on canned soups, cured meats, and other salty favourites, which can increase blood pressure, putting extra pressure on the kidneys.
COLD-WEATHER BLOOD PRESSURE SPIKES
Blood pressure is often “silent.” Unlike thirst (which reminds you to drink) or fatigue (which tells you to rest), high blood pressure has no clear symptoms until serious harm is done. That’swhy it’s the most important factor to watch closely in winter.
LESS MOVEMENT, SLOWER CIRCULATION
Staying indoors and moving less can affect how well your body processes fluids, leaving more work for your kidneys.
EXTRA BURDEN FROM ILLNESS
Winter infections like colds and flu increase waste in the body. Medications used to fight them can also add stress on the kidneys.
HORMONAL STRESS RESPONSE
Cold exposure stimulates the release of stress hormones like adrenaline and noradrenaline. These hormones prepare the body to conserve heat and energy, but they also raise blood pressure and alter kidney function. The kidneys must then adjust filtration and fluid reabsorption processes to cope with these hormonal changes.
VITAMIN D DEFICIENCY
Vitamin D supports strong bones and helps regulate calcium and phosphate. It is primarily produced by the body through exposure to sunlight, so with reduced sunlight hours it is important to ensure vitamin D levels remain steady.
WINTER ILLNESS REMEDIES
Pain relievers like ibuprofen and other NSAIDs (nonsteroidal anti-inflammatory drugs) can worsen kidney problems, while high doses of vitamin C can increase the risk of kidney stones.
Talk to your healthcare provider before taking new medicines or supplements.
Your kidneys work tirelessly year-round, but in winter, a little extra care can go a long way.
Drink water regularly, even if you don’t feel thirsty.
Choose lower-sodium versions of your favourite winter foods.
Keep active indoors with gentle exercise.
Monitor your blood pressure.
Talk to your healthcare provider if you notice swelling, changes in urination, or fatigue.
Why does cold weather raise blood pressure?
The kidneys’ primary role is to filter waste products and excess fluid from the blood, keeping the body’s internal environment balanced. To do this, they rely on a dense network of tiny blood vessels called glomeruli. These microscopic filters are delicate and highly sensitive to changes in blood pressure.
When blood pressure is consistently high, the force of blood flowing through these small vessels is stronger than normal. Over time, this constant strain causes the vessel walls to thicken and stiffen, reducing blood flow into the glomeruli. With less blood passing through, the kidneys cannot effectively remove toxins, regulate electrolytes, or maintain fluid balance.
As kidney function declines, waste products build up in the bloodstream, leading to symptoms like fatigue, swelling, and changes in urination. For people already living with CKD, even small seasonal spikes in blood pressure—like those commonly seen in colder months—can speed up this process. Winter-related increases in blood pressure may seem minor, but because the kidneys are already under strain, these fluctuations can tip the balance and contribute to further loss of kidney function.
The kidneys don’t just respond to blood pressure, they also help regulate it. When blood pressure rises, the kidneys have to adjust fluid and salt balance to bring it down. If they can’t keep up, blood pressure climbs higher, creating a vicious cycle.
By staying warm, monitoring blood pressure, making mindful food choices, and keeping up with healthy routines, people with kidney disease can reduce their risks and protect their kidney health all winter long.
Managing Your Blood Pressure in Cold Weather
Monitor Blood Pressure Regularly
Check your blood pressure at home, especially during colder months. Share your readings with your healthcare provider to see if adjustments are needed.
Dress Warmly and Stay Active
Keeping your body warm helps blood vessels stay relaxed. Even light indoor exercise like walking in place, stretching, or low-impact routines supports circulation and helps regulate blood pressure.
Manage Stress and Sleep
Shorter days and holiday pressures can raise stress, which also increases blood pressure. Relaxation techniques like meditation, deep breathing, or listening to calming music can help.
