Most kidney stones can pass on their own, but the odds depend almost entirely on size. Stones 1 to 4 millimeters in diameter pass naturally about 78% of the time, while 5-millimeter stones pass around 60% of the time. Stones 8 millimeters or larger drop to a 39% chance of passing without intervention. If your stone is in the passable range, several evidence-backed strategies can help speed things along and reduce your risk of forming new ones.
Drink Enough to Produce 2.5 Liters of Urine
Water is the single most effective tool for passing a kidney stone. The goal isn’t a specific number of glasses per day. It’s a specific urine output: 2.5 liters or more. For most people, that means drinking 3 to 4 liters of fluid spread throughout the day. In healthy adults under 50 who aren’t on any medications, up to 5 or 6 liters a day is safe as long as it’s consumed gradually rather than all at once.
Higher fluid volume keeps urine dilute, which does two things. It reduces the concentration of minerals that clump together to form stones, and it creates more urine flow to physically push an existing stone through the ureter. If you’re taking a diuretic for blood pressure or stone prevention, keep intake closer to 3 to 4 liters and have your sodium levels checked periodically, since overhydrating on diuretics can lower blood sodium to dangerous levels.
Use Citrus to Raise Urine Citrate
Citrate is one of the body’s natural defenses against kidney stones. It binds to calcium in urine, forming a soluble complex that prevents calcium from pairing with oxalate (the combination that creates the most common type of stone). Citrate also directly inhibits crystal formation, growth, and clumping.
Lemon juice is the most accessible source. A liter of lemonade daily, even made from powdered mixes high in potassium citrate like Crystal Light Lemonade, can raise urine pH and increase citrate levels meaningfully. Fresh-squeezed lemon juice diluted in water works too. The key is consistency: a glass once in a while won’t change your urine chemistry. Daily intake over weeks and months is what shifts the balance.
Eat More Calcium, Not Less
This surprises most people. Since about 80% of kidney stones contain calcium, the instinct is to cut calcium from your diet. That instinct is wrong. Dietary calcium actually protects you by binding to oxalate in your digestive tract before it ever reaches your kidneys. Without enough calcium in your gut, more oxalate gets absorbed into your bloodstream and filtered through your kidneys, where it can crystallize into stones.
The target is 1,200 milligrams of calcium daily, ideally from food rather than supplements. Spreading calcium-rich foods across each meal is more effective than loading up at one sitting, because you want calcium present in your gut whenever you’re eating oxalate-containing foods. Dairy, fortified plant milks, canned sardines, and leafy greens (other than spinach) are all good sources.
Manage Oxalate Intake Strategically
You don’t need to eliminate oxalate entirely, but knowing which foods pack the biggest punch helps you make smarter choices. Half a cup of boiled spinach contains a staggering 547 milligrams of oxalate, and even a cup of raw spinach has 316 milligrams. For comparison, an ounce of roasted almonds has 72 milligrams and a tablespoon of almond butter has about 42 milligrams.
The practical move isn’t avoiding all of these foods forever. It’s pairing high-oxalate foods with calcium-rich ones at the same meal so the oxalate gets bound in your gut. If you love spinach salads, add cheese or yogurt on the side. If almonds are your go-to snack, have them with milk. This pairing strategy lets you keep eating foods you enjoy while reducing the amount of oxalate that reaches your kidneys.
Cut Back on Sodium
Sodium and calcium are linked in the kidneys: the more sodium you excrete, the more calcium gets pulled into your urine along with it. High urinary calcium is one of the primary drivers of stone formation. The National Kidney Foundation recommends keeping sodium intake around 2,300 milligrams per day, which is roughly one teaspoon of table salt. Most people exceed this without realizing it, since processed foods, restaurant meals, and condiments are loaded with hidden sodium.
Lemon Juice, Apple Cider Vinegar, and Chanca Piedra
Three natural remedies dominate online discussions about kidney stones. Here’s what the evidence actually shows for each.
Lemon juice has the strongest backing. Its citrate content is well-established as a stone inhibitor, and the mechanism is clearly understood. It won’t dissolve an existing stone sitting in your ureter, but it can slow growth and help prevent new ones.
Apple cider vinegar has been shown to reduce stone-related changes in rats, with improvements in kidney tissue and urinary mineral levels. The proposed mechanism involves plant compounds that reduce inflammation and act as antioxidants. No human clinical trials have confirmed these effects, though, and no reliable human dosage exists. If you want to try it, a tablespoon or two diluted in water is unlikely to cause harm, but don’t count on it as your primary strategy.
Chanca piedra (a tropical plant also called Phyllanthus niruri) has more promising human data. In a clinical trial of 150 patients with calcium oxalate stones, those who took the extract daily for at least three months after a stone-breaking procedure had significantly better clearance rates, especially for stones in the lower part of the kidney: 93.7% became stone-free compared to 70.8% in the control group. No side effects were observed. It appears to help the body clear stone fragments rather than dissolving intact stones, and it’s available as a supplement in most health stores.
What Happens While You Wait
Passing a stone typically takes days to weeks, and smaller stones can sometimes pass in hours. The pain comes in waves as the stone moves through the ureter, the narrow tube connecting your kidney to your bladder. Once it drops into the bladder, the worst is over. Passing it from the bladder out through the urethra is usually painless or mildly uncomfortable.
During this time, staying active can help. Walking and gentle movement encourage the stone to shift downward. Staying sedentary doesn’t help and may slow progress. Over-the-counter pain relief can make the process tolerable, and a warm bath or heating pad on your lower back or side can ease muscle spasms around the ureter.
Signs That Natural Passage Isn’t Working
Not every stone will pass on its own, and waiting too long with a stuck stone carries real risks. A stone blocking urine flow can cause the kidney to swell (a condition called hydronephrosis), lead to kidney infection, or even cause acute kidney injury. If you haven’t passed the stone within four to six weeks, follow up with your provider. They’ll likely recommend a procedure to break it up or remove it.
Go to the emergency department if the pain becomes unbearable, you develop a fever or chills (signs of infection), you can’t keep fluids down due to vomiting, or you stop producing urine entirely. These situations mean the stone is causing complications that natural methods can’t resolve.