Most kidney stones pass on their own, especially smaller ones. Stones under 4mm in diameter pass without intervention about 78% of the time, while stones between 5 and 7mm still have a 60% passage rate. The key factors you can control are hydration, movement, pain management, and diet. How long it takes depends almost entirely on stone size: tiny stones (2mm or less) pass in about 8 days on average, while stones 4mm and larger can take around 22 days.
Your Stone Size Determines the Plan
Before trying to pass a stone naturally, you need to know how big it is. Your doctor can measure this with a CT scan. The numbers tell a clear story: stones 1 to 4mm pass on their own about 78% of the time, stones 5 to 7mm pass about 60% of the time, and stones 8mm or larger drop to a 39% success rate. If your stone is on the larger end, your doctor may prescribe a medication that relaxes the ureter (the tube between your kidney and bladder) to help the stone move. In pooled data from eight clinical trials, this type of medication improved passage rates from 66% to 85% for stones between 4 and 10mm. For stones under 4mm, the medication made no difference because those small stones already pass easily.
If your stone is larger than 10mm, natural passage is unlikely and waiting too long risks complications. For stones in the passable range, the strategies below can make a real difference in how quickly and comfortably the stone moves through.
Drink More Water Than You Think You Need
Hydration is the single most important thing you can do. The goal is to flush the stone through your urinary tract by producing a high volume of urine. Aim for at least 2 liters (8 cups) of water per day, and ideally 3 liters (12 cups). If you’re sweating from heat or exercise, you need even more, because sweat reduces urine output. A good way to gauge whether you’re drinking enough is your urine color. It should be pale yellow or nearly clear. If it’s dark, you’re behind.
Spread your water intake throughout the day and night. Stones can shift position at any time, and consistent hydration keeps the pressure behind the stone steady. Some people set a timer to remind themselves to drink every hour.
Add Lemon to Your Water
Lemon juice is a natural source of citrate, a compound that helps prevent calcium-based stones from growing larger and may help break down their surface. About 85cc of lemon juice (roughly a third of a cup) contains a meaningful dose of citrate. The exact amount needed to make a clinical difference is still being refined, but mixing fresh lemon juice into your daily water is a low-risk strategy that many urologists recommend. A reasonable approach is squeezing half a lemon into each liter of water you drink. This also makes it easier to hit your hydration targets if you find plain water boring.
Stay Active and Upright
Movement helps. Walking, light jogging, and climbing stairs all use gravity to encourage a stone to migrate downward through the ureter. There’s no formal clinical trial proving that one exercise is better than another, but staying sedentary works against you. The general principle is simple: a stone in a moving body has more opportunities to shift than a stone in a body lying on the couch.
One quirky but well-publicized study tested this principle using a silicone kidney model on a roller coaster at Walt Disney World. Riding in the back of the coaster resulted in a 64% stone passage rate compared to 17% in the front. The vibrations, jerking movements, and changes in gravitational force all contributed. You don’t need a theme park, but the takeaway is that varied physical movement, even bumpy or jarring activity, can genuinely help dislodge small stones.
Managing Pain While You Wait
Kidney stone pain can be intense, and managing it well matters not just for comfort but for your ability to keep drinking fluids and staying mobile. Anti-inflammatory pain relievers like ibuprofen are the best first choice. A large meta-analysis found that NSAIDs provide the most sustained pain relief for kidney stone episodes, with fewer side effects than stronger painkillers. They also reduce the ureteral swelling that contributes to the pain, which is something acetaminophen (Tylenol) does not do. Patients who took NSAIDs also needed less backup pain medication compared to those who took acetaminophen.
A warm bath or a heating pad on your lower back or side can also help with muscle spasms in the area around the ureter. Some people find that alternating heat with gentle walking provides the best relief during acute pain episodes.
What to Eat and Avoid
Most kidney stones are calcium oxalate stones. While the stone is actively passing, reducing high-oxalate foods won’t shrink the stone you already have, but it can prevent the stone from growing and help you avoid forming new ones. The biggest dietary oxalate sources to cut back on are spinach, nuts and nut products (including peanuts), rhubarb, and wheat bran.
A common misconception is that you should avoid calcium. The opposite is true. Dietary calcium binds to oxalate in your gut before it ever reaches your kidneys, so eating calcium-rich foods like yogurt or cheese with meals actually reduces your stone risk. Just avoid calcium supplements taken between meals, as these can raise urinary calcium levels. Reducing your sodium intake also helps, since excess salt increases the amount of calcium your kidneys filter.
Catch the Stone When It Passes
This step is easy to forget in the relief of finally passing a stone, but it’s one of the most valuable things you can do. Knowing what your stone is made of lets your doctor give you specific dietary and medical advice to prevent the next one, and about half of people who get a kidney stone will get another within five to ten years.
Use a kidney stone strainer, a small mesh or gauze filter you can buy at most pharmacies or get from your doctor’s office. Place it over the toilet or urinal and filter every single time you urinate. The stone can pass at any hour, and it may be as small as a grain of sand, so check the strainer carefully each time. When you find it, place it in a clean, dry container with a lid. Don’t wrap it in tissue, tape, or add any liquid. Bring the container to your doctor for laboratory analysis.
How Long the Process Takes
Patience is genuinely part of the treatment. Stones 2mm or smaller pass in about 8 days on average. Stones between 2 and 4mm take roughly 12 days. Stones 4mm and larger average about 22 days. These are averages, and for 95% of stones to pass, the window extends to about 31 to 40 days depending on size.
If your stone hasn’t passed within four to six weeks, follow up with your provider. At that point, the risk of complications from a prolonged blockage starts to outweigh the benefits of waiting.
Signs That Natural Passage Isn’t Working
Certain symptoms mean you should stop waiting and get medical help promptly. Fever or chills suggest an infection behind the blockage, which can become dangerous quickly. Inability to urinate means the stone is causing a complete obstruction. Persistent vomiting can lead to dehydration, which makes everything worse. Cloudy, foul-smelling, or bloody urine can signal infection or significant tissue irritation. And if the pain becomes truly unbearable and isn’t responding to over-the-counter medication, that’s reason enough to go to an emergency department. A stone that seemed passable on imaging can still get stuck in a narrow section of the ureter, and waiting too long with a full blockage can damage the kidney.