Urine pH can help your doctor diagnose certain diseases and disorders and can also tell you a lot about your diet. Urine pH is important when it comes to monitoring your risk of kidney stones, as extreme pH levels can cause stones to form. Read on to see what urine pH can reveal about your health and what you can do to improve your levels.
What is Urine pH?
pH is a measure of how acidic or alkaline (basic) a fluid is. A pH of 7 is considered neutral. Below 7 fluids are acidic, while above 7 they are alkaline.
Every fluid in the body has a unique pH range that is optimal for health. For example, blood pH is usually maintained in a tight range between 7.35 and 7.45. Even a slight increase or decrease in blood pH can be dangerous. Saliva normally has a pH range of 6.2-7.6, which neutralizes acids in foods and prevents bad bacteria from growing [1, 2, 3].
The kidneys help keep the blood pH from going too low or too high by filtering acids or alkaline compounds (bicarbonate) from the blood and releasing them in the urine. That’s why the urine has a wider pH range compared to both blood and saliva. The normal range of urine pH is between 4.5 and 8 [4, 5].
Diet, certain drugs, infections, and poor kidney function can all affect the pH of urine. For example, diets high in protein from meat, fish, dairy, and grains can decrease urine pH (more acidic), whereas diets high in fruits and vegetables can increase urine pH (more alkaline) [6, 7, 8].
Urine pH Testing
Urine pH is tested as part of a routine urinalysis. It is often used to assess the risk of kidney stones, help diagnose urinary tract infections (UTIs), or determine the effectiveness of some antibiotics and other drugs that can be affected by urine pH [9, 10, 11].
Dipstick vs. Electrode
Urine pH can be measured using a dipstick, which is a test strip that is placed in a urine sample and reveals the pH depending on how the color of the strip changes.
The advantages of dipstick measurements include convenience, cost, and the ability to test pH at home. However, they are not as accurate as an electrode measurement and studies suggest they shouldn’t be used for clinical decision-making [12, 13].
The gold standard of measuring urine pH is a pH meter that uses an electrode. It is much more accurate, however, it is also more expensive [12].
Fasting vs. Spot vs. 24-Hour Test
For a routine urinalysis, a urine sample is provided after an overnight fast. This is referred to as a fasting urine sample. A morning sample is usually more alkaline [14].
A spot urine sample is a random sample taken during the day.
Urine pH is known to change throughout the day, peaking in the middle of the day, and decreasing after each meal. To get an accurate measurement of the average urine pH throughout the day, 24-hour urine tests are used [15].
Fasting and single-spot samples are not accurate enough to assess and treat people with kidney stones [16, 14].
Normal Urine pH levels
Lab results are commonly shown as a set of values known as a “reference range”, which is sometimes referred to as a “normal range”. A reference range includes the upper and lower limits of a lab test based on a group of otherwise healthy people.
Your healthcare provider will compare your lab test results with reference values to see if any of your results fall outside the range of expected values. By doing so, you and your healthcare provider can gain clues to help identify possible conditions or diseases.
The normal range for urine pH is between 4.5 and 8 [4, 5]. Urine pH is slightly more alkaline in the morning than at night. Women also tend to have slightly higher urine pH levels than men [14, 17, 18].
Improper storage conditions (high temperatures) before analysis can result in urine pH levels above 9, so if you see levels that are abnormally high you may want to retest to be sure [19].
Factors that Can Decrease Urine pH
Causes shown below are commonly associated with this low urine pH. Work with your doctor or other health care professional for an accurate diagnosis.
1) Diet
Food is one of the most important factors in determining the pH of urine. Meat, fish, dairy, and grains all increase the number of acids that the kidney has to filter into the urine. Most vegetables and fruits (especially citrus) generate alkaline compounds, reducing the number of acids the kidneys must filter [20].
A study in over 22k people has shown that high fruit and vegetable intake and lower consumption of meat were linked to a more alkaline urine [8].
Protein increases the amount of acid produced in the body. Kidneys have to filter these acids into the urine, decreasing its pH. Three studies with a total of 89 people revealed that high protein diets make the urine more acidic [21, 22, 23].
Two studies with 18 and 26 people, respectively, reported that people who ate a diet high in meat and protein over three days saw their urine pH drop, while those who ate a diet high in vegetables and fruits and low in meats saw their urine pH increase [24, 25].
2) Diarrhea
Diarrhea causes a loss of electrolytes, thereby reducing blood pH (i.e. making it more acidic). The kidneys then compensate for this by releasing more acids in the urine [26].
A study in 24 people reported that diarrhea reduced urine pH from 6.7 to 5.5 on average [26].
3) High Blood Sugar and Diabetes
High blood sugar causes insulin resistance. This causes the kidneys to produce less ammonia, a compound that increases the pH of the urine [27].
In a study of 5k people, higher blood sugar levels were associated with lower urine pH. Similarly, another study of 1k people found that those with urine pH below 5.5 also tended to have the highest degree of insulin resistance [28, 29].
Conversely, in a five-year-long observational study of 3.1k people those with a urine pH lower than 5.5 had a 2.5 times higher risk of developing diabetes than those who’s urine pH was above 6.5 [30].
3) Poor Kidney Function
Studies suggest that people with impaired kidney function or kidney disease may have lower urine pH [31, 32].
Mercury, for example, is a toxin that damages the kidneys [33]. In a study of 200 workers who were constantly exposed to mercury, urine pH decreased with kidney dysfunction and increasing levels of mercury in the urine [34].
4) Acid/Base Disorders
When there are acid/base disorders in the body that turn blood more acidic (e.g. diabetic ketoacidosis, respiratory acidosis, rhabdomyolysis), kidneys try to compensate by increasing the excretion of acids in urine, thereby turning the urine more acidic [35, 36].
5) Certain Drugs
Some drugs, such as water pills (diuretics) can make the urine more acidic [37, 38, 39].
6) Genes
While urine pH is largely dependent on external factors such as diet and health conditions, studies suggest that genes also play their part [40, 41]. You can find more information about particular genes and SNPs that have been associated with urine pH at the bottom of this article.
Conditions Associated with Low Urine pH Levels
1) Kidney Stones
Low urine pH facilitates the formation of kidney stones. Acidic urine causes uric acid and calcium oxalate to clump together and form stones. This effect is seen with pH levels below 5.5 [25, 42, 24, 43, 44, 45].
2) Obesity and Excess Body Weight
Obesity and high BMI are linked to an increased risk of kidney stones. This may be due to reduced urine pH in obese and overweight people [46].
A study in 460 men with kidney stones reported that higher BMI was associated with a lower urine pH levels [47].
Similarly, in a study of 342 people, urine pH was lower in obese and overweight people compared to normal body weight individuals [48].
However, a larger study with 13,895 men found a link between urine pH below 5.5 and obesity in men, but not in women [49].
3) Metabolic Syndrome
Metabolic syndrome is a condition characterized by at least three of the following five features: high blood pressure, high blood sugar, excess stomach fat, high triglycerides, and low HDL cholesterol (HDL-C).
In a study of 5.4k people, those with metabolic syndrome had lower urine pH than those without it. People with a urine pH below 5.5 were 50% more likely to have metabolic syndrome than those with a pH above 6 [50].
Additionally, in a three-year-long study with 14.5k healthy people, having a urine pH below 5.5 was linked to a 48% increased risk of developing metabolic syndrome compared to a pH above 6 [51].
There are several other studies that also found a link between metabolic syndrome and its components and lower urine pH levels [52, 53, 49].
4) Non-alcoholic Fatty Liver Disease
Non-alcoholic fatty liver disease (NAFLD) is a buildup of fat in the liver due to causes other than excessive alcohol (diet, infections, drugs).
In a study of 1k people, a urine pH below 5.5 was associated with a higher likelihood of having NAFLD compared to a pH above 5.5 [54].
Another study of 98 people found that a urine pH below 6 was linked to fatty buildup in the liver [53].
5) Advanced Chronic Kidney Disease
In a study of 1.8k people, those with urine pH between 5 and 5.5 had a 32% higher risk of developing advanced chronic kidney disease over the next 8 years [55].
6) Bladder Cancer
A study in over 700 bladder cancer patients and 611 controls found a link between bladder cancer and lower pH (<5) [6].
Ways to Increase Urine pH Levels
The most important thing is to work with your doctor to find out what’s causing your low urine pH and to treat any underlying conditions. The additional lifestyle changes listed below are other things you may want to discuss with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!
If you are at risk of kidney stones, your doctor may prescribe drugs or supplements that can increase the pH of your urine [56].
1) Diet
Urine that is more acidic than normal may indicate a low fruit and vegetable intake. An easy way to fix this would be to decrease the consumption of meat, fish, and dairy, while increasing vegetables and fruits. Studies suggest that a diet rich in fruits and vegetables is associated with more alkaline urine pH [7, 8, 21, 22, 23].
In addition, according to research, dietary changes may produce effects relatively rapidly. Two studies in which people (18 and 26, respectively) were put on alkaline diets saw their levels increase over the next three days [24, 25].
As high-protein diets decrease urine pH levels, avoiding protein supplements may also be beneficial [21, 22, 23].
2) Foods Rich in Citric and Malic Acid
Studies suggest that foods that may be especially beneficial for increasing urine pH are those rich in citric and malic acid [57, 58, 59, 60].
Foods rich in citric acid, include fruits such as citrus fruits, blackcurrant, and melon. Foods rich in malic acid include apples, pears, and apple cider vinegar.
Factors that Can Increase Urine pH
Causes shown below are commonly associated with this high urine pH. Work with your doctor or other health care professional for an accurate diagnosis.
1) Urinary Tract Infection
The most common cause of elevated urine pH levels is an infection in the urinary tract. Many of these infectious organisms produce an enzyme called urease that breaks apart urea to carbon dioxide and ammonia, increasing urine pH [61, 62].
2) Vomiting
Vomiting causes blood pH to increase, which the kidneys must counteract by releasing alkaline compounds into the urine. This increases urine pH and makes it more alkaline [63].
3) Endurance Exercise
Studies suggest that urine pH increases shortly after strenuous exercise [64].
4) Acid/Base Disorders
When there are acid/base disorders in the body that turn blood more alkaline (e.g. respiratory alkalosis), kidneys try to compensate by increasing the excretion of bases in urine, thereby turning the urine more alkaline.
Respiratory alkalosis is a condition caused by low carbon dioxide levels in the blood due to breathing at a very fast rate (hyperventilation). It is usually caused by critical illness but can also be caused by many heart and lung disorders [65].
5) Kidney Disease
People with certain types of kidney disease may have elevated urine pH.
Renal tubular acidosis (RTA) is a group of disorders that change how the kidneys handle the balance between acids and bases. They can be caused by mutations, autoimmune diseases such as lupus and rheumatoid arthritis, toxins, and chronic kidney disease. People with RTA commonly have elevated urine pH due to an inability to release acids in the urine [66, 67].
6) Certain Drugs
Some drugs, including anti-seizure drugs, acetazolamide can increase urine pH levels [68, 69, 70, 69].
7) Genes
While urine pH is largely dependent on external factors such as diet and health conditions, studies suggest that genes also play their part [40, 41]. You can find more information about particular genes and SNPs that have been associated with urine pH at the bottom of this article.
Conditions Associated with High Urine pH Levels
1) Kidney Stones
The risk of calcium phosphate kidney stones increases as the urine pH rises from 6.5 to 7.5. High urine pH causes calcium phosphate to become concentrated and clump together [71, 14, 72, 73, 45].
In a study of 1.2k people with stones, those with the highest urine pH levels tended to have the most calcium phosphate stones [74].
In another study of 4.7k people who initially had calcium oxalate stones, those who had higher urine pH were more likely to later develop calcium phosphate stones [75].
Ways to Decrease Urine pH Levels
The most important thing is to work with your doctor to find out what’s causing your high urine pH and to treat any underlying conditions. The additional lifestyle changes listed below are other things you may want to discuss with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!
If you are at risk of kidney stones, your doctor may prescribe drugs or supplements that can acidify your urine.
1) Prevent Urinary Tract Infections
Studies suggest that cranberries and cranberry products may help prevent urinary tract infections (UTIs) and decrease urine pH [76, 77, 78, 79].
Genetics of Urine pH
SNPs that have been associated with higher urine pH [40]:
- rs6955765 (T>C)
- rs145048940 (C>A)
- rs34447434 (A>C)
- rs17761305 (T>C)
- rs28623722 (G>A)
- rs28370990 (T>C)
- rs17183073 (C>G)
- rs768831 (A>G)
- rs1713968 (A>G)
- rs116189043 (A>G)
- rs1611781 (G>A)
- rs6554409 (C>T)
- rs1713961 (C>T)
- rs1718883 (T>A)
- rs7670536 (T>C)
- rs1713962 (G>A)
- rs1718874 (C>T)
- rs1713967 (T>A)
- rs1718873 (C>T)
- rs13107451 (A>G)
- rs11726321 (C>T)
- rs77053948 (G>A)
- rs1718834 (T>C)
- rs1718872 (C>G)
- rs6817232 (G>C)
Polycystic kidney disease is a genetic disorder that causes low urine pH and is caused by the PKHD1 gene and mutations in PKD1 or PKD2 genes [80].
Genes that have been Associated with Renal Tubular Acidosis
Renal tubular acidosis, which results in alkaline urine, has been associated with mutations in the following genes [41+]:
