Kidneys filter blood to remove waste products from blood to make urine. When these waste products contain crystal-forming substances such as calcium, oxalate and uric acid and there is less fluid to dissolve them. Then these crystals combine and become hard over time to turn as kidney stones.
Males are more prone to develop kidney stones than females. People between the ages of 20 and 50 years likely to occur kidney stones. 
Kidney stones can cause many problems such as pain in the back, burning during urination, blood in the urine, vomiting, and nausea etc. and can affect any part of the urinary tract.
Risk Factors of Kidney Stones
Dehydration is the greatest risk factor for forming kidney stones. Lack of water makes the body to produce a very low volume of urine per day. Not having enough water to dissolve salts makes the urine more acidic, creating an ideal environment for kidney stones.
Drinking 3 liters of fluid to make at least 2.5 liters of urine per day can reduce the risk of getting kidney stones. 
Diets that are high in protein and sodium but low in calcium can increase the risk of some types of kidney stones. Too much salt in the diet prevents the reabsorption of calcium from the urine which leads to kidney stones formation. Eating foods rich in oxalate can also increase the risk of forming kidney stones.
High body mass index (BMI), waist circumference and weight gain have been linked to an increased risk of kidney stones. 
A family history of kidney stones is also one of the factors to develop them.
What is Apple Cider Vinegar?
Apple cider vinegar or ACV is a type of vinegar produced after the fermentation of apple juice. It passes through two steps fermentation process. The result produces acetic acid, which is considered as the main ingredient of ACV.
Nutritional Fact of ACV: 
- Acetic Acid
- Citric Acid
- Vitamin B-6
- Probiotics and Enzymes
Due to the presence of many health beneficial constituents in ACV, it can be used as one of the remedies to reduce or eliminate the kidney stones.
The acetic and citric acid, vitamin B-6, and potassium in ACV are believed as the reasons to dissolve kidney stones. It also maintains the pH level of blood and enhances the calcium observation which helps in reducing kidney stones.
What Research Says about ACV for Kidney Stones?
In a study published in Wiley Online Library, suggested that fermented vinegar may reduce the formation of kidney stones.
In another study at EBioMedicine in July 2019 observed that daily vinegar consumption linked to a lower risk of kidney stones formation and reduced stone recurrence.
Researchers found that vinegar significantly increased urine citrate excretion, a well-known inhibitor of oxalate crystallization, and decreased urine calcium excretion which is a component of oxalate crystal formation.
How Apple Cider Vinegar Treats Kidney Stones?
1. Cleanses the Body
Apple cider vinegar has a disinfecting properties and acts as a natural bad germ fighter. As a result, it helps the body to get rid of the harmful toxins from the body and prevents the formation and recurrence of kidney stones.
2. Increases Urine Citrate Levels
Citric Acid helps to soften, and break down kidney stones so that it can dissolve and easily pass through urine.
Citric acid combines with urinary calcium and reduces the supersaturation of urine. Also, it can bind with calcium oxalate crystals and prevents crystal growth. 
Apple cider vinegar, being a rich source of citric acid, can help to increase the citrate level in the urine which, as a result, helps to dissolve kidney stones.
3. Balances the pH of the Urine
The acidic and basic condition of the body plays an important role to affect the pH of urine. Besides, highly acidic or basic/alkaline condition tends to the formation of kidney stones.
According to the American Association for Clinical Chemistry, the normal urine pH is slightly acidic with a value of 6.0, but it can range from 4.5 to 8.0.
Apple cider vinegar has been recommended to restore alkaline acid balance and can balance the body’s pH in a short amount of time. 
Thus, including apple cider vinegar to the diet will help to balance the pH of the body. As a result, it can dissolve the kidney stones.
4. May Reduce Oxalate Formation in the Urine
Calcium oxalate stones are the most common type of kidney stone. Oxalate is a chemical, naturally found in most foods and is also made daily by the liver. 
If the oxalate levels become too high, the extra oxalate can combine with calcium to form kidney stones.
Vitamin B-6 (pyridoxine) can reduce the risk of oxalate formation in the urine. 
Vitamin B-6 helps alanine glyoxylate aminotransferase (AGT), which is an enzyme, to accelerate the conversion of glyoxylate to glycine. Deficiency of AGT or low levels of Vitamin B-6 may cause glyoxylate to convert into oxalate and may increase the level of oxalate in the urine.
As apple cider vinegar contains a trace amount of vitamin B-6, it may reduce the formation of oxalate in the urine. As a result, it may reduce the further growth of kidney stones.
5. Enhances Calcium Absorption
Low calcium in the diet will increase the chances of the formation of calcium oxalate stones. But taking an appropriate amount of calcium as per the age may help to reduce that risk. 
Apple cider vinegar catalyzes the calcium absorption in the body after having a meal containing calcium.
A test performed on the rat model showed an improvement in calcium absorption. This enhanced calcium absorption was believed due to the improved calcium solubility and the presence of acetic acid. 
More human research required to prove the effect of apple cider vinegar to improve calcium absorption on humans.
6. May Reduce the Supersaturation of Urine
Urine is often supersaturated with stone-forming substances such as calcium oxalate, calcium phosphate, and uric acid. 
So, the chances of developing kidney stones increases.
On the other side, Potassium intake has been reported to reduce the supersaturation of urine. 
Potassium does so by increasing the level of urinary citrate, urine volumes and maintaining the pH level of urine. As a result, it reduces the relative supersaturations of calcium oxalate and uric acid, despite higher urinary excretion of oxalate.
Apple cider vinegar is rich in Potassium. So, it can reduce the chances of developing kidney stones.
How much Apple Cider Vinegar for Kidney Stones?
Although apple cider vinegar is beneficial in removing kidney stones. But it should not be taken in undiluted form. Due to its acidic nature, it can weaken tooth enamel which leads to tooth decay and can burn the throat.
Diluting it or using it as an ingredient in a meal can reduce these risks. The simplest way to dilute apple cider vinegar is to take 1-2 full spoons (15-30 ml) of ACV and mix it with a large glass of water. Take this regularly before or with the meal.
Adding 1 tablespoon of raw honey and 1 tablespoon lemon juice can enhance the flavor and can provide extra health benefits.
Add ACV with olive oil as a salad dressing of a mixture of leafy greens and cucumbers.
Also Read: 09 Proven Essential Oils for Kidney Stones