Fasting With Kidney Stones or Recurrent UTIs: What a Urologist Wants You to Know Before the Next Vrat

Every Navratri, and again before Karwa Chauth, Ekadashi and a long list of other fasts, a few patients ask me the same question: "Doctor, can I fast?" Some ask it honestly. Others ask it already knowing the answer they want.

I do not tell patients to stop fasting. Fasting is part of how many families live their faith, and it is not my place to argue with that. What I can do is explain what a long gap without fluids does to a kidney that forms stones or a bladder that gets infected easily, so that you can decide with the facts in front of you.

What Happens When You Drink Less

Kidney stones form when minerals in the urine become too concentrated and begin to crystallise. The simplest way to keep them dissolved is to pass a large volume of dilute urine. Most stone formers are advised to pass about two to two and a half litres of urine a day, which usually means drinking more than that.

When you fast and cut down on water, your body holds on to fluid and the urine that does come out is dark and concentrated. For someone who has never had a stone, a day of this is usually harmless. For someone who has already formed stones, or who still has a small stone sitting in the kidney, it is exactly the condition stones grow in.

The bladder has a similar problem. Passing urine regularly flushes out bacteria before they can settle in. Long gaps with little fluid mean less flushing, and people who get frequent urinary infections often notice a flare-up within a day or two of a fast.

Who Should Speak to a Doctor Before Fasting

Please ask first if any of these is true for you:

• You have had kidney stone pain in the last few weeks, or you know you still have a stone.
• You have a ureteric stent in place.
• You have had two or more urinary infections in the last year, or an infection that is not fully treated.
• You have only one working kidney, or your kidney function is reduced.
• You take tablets for blood pressure, water tablets (diuretics), or any medicine meant to prevent stones.

If you have a stone that is blocking the flow of urine, or an infection with fever, fasting is not the time to test your limits. Treat first, fast later.

How to Fast More Safely

Many vrats allow water, milk, buttermilk, coconut water, lemon water, and fruit. If yours does, use that. Drink steadily through the permitted hours instead of finishing a litre at once, because the kidneys cope better with a steady supply.

If your fast allows no water at all for part of the day, drink generously before you begin and as soon as it ends. The pre-dawn meal and the evening break are when you can make up the most ground, so do not waste them on tea and fried food.

What About the Fasting Food Itself

This is the part nobody talks about. Many popular fasting foods are harder on a stone-forming kidney than people expect.

Rock salt (sendha namak): It is sodium chloride, the same thing as table salt. Swapping one for the other does not reduce your sodium, and sodium raises the amount of calcium passing into the urine. Go easy on both.

Potato, sweet potato, peanuts and nuts: These are among the higher-oxalate foods, and oxalate is what the commonest kind of kidney stone is made of. Fasting plates are often built almost entirely from them. Buckwheat flour (kuttu) also contains a meaningful amount of oxalate.

Tea and coffee: They add oxalate as well and tend to replace water. Keep them to a cup or two, and not in place of a glass of water.

You do not have to give up your vrat food. Have smaller portions, pair them with a calcium source such as curd or milk (calcium taken with the meal binds oxalate in the gut), add fruit and cucumber, and keep the salt light.

When to Break the Fast and Get Help

Breaking a fast because of illness is not a failure of faith. Please stop and seek medical care if you have:

• Severe pain in the side or back that comes in waves, or pain that does not ease.
• Fever or chills, especially together with pain or burning when you pass urine.
• Repeated vomiting, so you cannot keep water down.
• Blood in the urine, or passing almost no urine for many hours.
• Dizziness or fainting.

Fever with stone pain should never wait until the fast is over. An infected kidney that cannot drain is an emergency.

If you are unsure whether your fast is safe, a short consultation before it begins is much easier than managing a stone attack in the middle of it. For more on what to do if pain starts suddenly, read What To Do When Kidney Stone Pain Strikes Suddenly, and for everyday prevention see Kidney Stones and Diet.