The answer depends on which pH you’re trying to lower, because your body doesn’t have a single pH level. Your blood, urine, skin, stomach, and vaginal fluid each maintain different pH ranges, and the strategies for shifting each one are completely different. In most cases, what people actually want is to restore a normal, healthy acidity that has drifted too alkaline, not to push their body into dangerous territory.
Here’s a quick orientation: a pH below 7 is acidic, and above 7 is alkaline. Blood pH sits in a tight range around 7.35 to 7.45. Urine pH fluctuates between about 4.5 and 8.0 depending on diet. Vaginal pH for women of reproductive age is normally 3.8 to 5.0. Skin surface pH hovers around 4.5 to 5.5. Each of these has its own biology and its own set of practical tools.
Why You Can’t (and Shouldn’t) Lower Blood pH
Your blood pH is the one number you cannot meaningfully change through diet or supplements. The body regulates it with extraordinary precision. Your lungs adjust how much carbon dioxide you exhale, and your kidneys fine-tune how much acid or bicarbonate they release into urine. When blood becomes even slightly too alkaline, specialized cells in the kidneys secrete bicarbonate into the urine to bring things back down. This system operates automatically, and it’s powerful enough to override anything you eat or drink.
If your blood pH is genuinely too high (a condition called alkalosis), that’s a medical problem with symptoms like muscle twitching, numbness or tingling in the hands and face, lightheadedness, nausea, and confusion. Severe cases can cause irregular heartbeats or coma. This isn’t something you treat at home. It’s typically caused by prolonged vomiting, certain medications, or kidney dysfunction, and it requires professional evaluation.
The “alkaline diet” trend has led many people to believe they need to change their blood pH through food. They don’t. What food changes is your urine pH, not your blood pH. Those are very different things.
How Diet Changes Urine pH
Urine pH is the measurement most responsive to what you eat, and it’s the one most people can actually influence. If you need a more acidic urine (lower pH), the general strategy is to eat more protein-rich foods and fewer fruits and vegetables. If that sounds counterintuitive, here’s why: when your body breaks down protein, it produces acid as a byproduct. Your kidneys then dump that acid into your urine, making it more acidic.
Researchers use a scoring system called PRAL (potential renal acid load) to estimate how much acid or base a food generates after digestion. Foods with high PRAL scores make urine more acidic. Hard cheeses top the list at roughly 23.6 milliequivalents per 100 grams. Meat, fish, eggs, and grains also score positive, meaning they push urine toward acidity. Fruits, vegetables, and juices sit at the opposite end, around negative 3 milliequivalents per 100 grams, making urine more alkaline.
One detail trips people up: citrus fruits taste acidic but actually make your urine more alkaline. Your body metabolizes the citrate in lemons, oranges, and limes into bicarbonate, which raises urine pH. So if your goal is to lower urine pH, eating more lemons will work against you.
A Japanese study that tested this directly found that an acidic diet (high in protein, low in fruits and vegetables) contained more than twice the acid-generating amino acids of an alkaline diet: 124 millimoles per day versus 57. The dietary shift produced measurable changes in urine acidity.
When Lowering Urine pH Matters
The main reason someone would want more acidic urine is to prevent certain types of kidney stones. Calcium phosphate and struvite stones form more easily in alkaline urine. Some urinary tract infections also thrive when urine is less acidic. Your doctor may recommend dietary changes or specific supplements to keep your urine in a target pH range, which you can track at home with simple test strips.
Restoring Vaginal Acidity
A healthy vaginal pH for women of childbearing age falls between 3.8 and 5.0, maintained primarily by beneficial bacteria that produce lactic acid. When that pH climbs above 4.5, it often signals a shift in the vaginal microbiome, commonly associated with bacterial vaginosis or yeast overgrowth. Unprotected sex, certain medications, hormonal changes, and douching can all push vaginal pH higher.
Lactic acid is the cornerstone of vaginal acidity. Beyond simply lowering pH, it actively works against harmful bacteria and even certain sexually transmitted pathogens through mechanisms that go beyond acidity alone. It also has anti-inflammatory effects, calming the immune response in vaginal tissue. Several over-the-counter vaginal gels and suppositories contain lactic acid specifically to help restore normal acidity.
Boric acid suppositories are another widely used option, particularly for recurrent bacterial vaginosis or yeast infections that don’t respond to standard treatments. These are inserted vaginally (never taken by mouth) and work by creating an environment hostile to the organisms causing the imbalance. Practical steps that support healthy vaginal pH include wearing breathable cotton underwear, avoiding scented soaps or washes near the vulva, and limiting unnecessary antibiotic use when possible.
Lowering Stomach pH
Some people produce too little stomach acid, a condition called hypochlorhydria. Symptoms often overlap with those of excess acid: bloating, heartburn, feeling overly full after small meals, and poor digestion. When the stomach isn’t acidic enough, it struggles to break down food properly, which can impair nutrient absorption.
The most common supplement used to increase stomach acidity is betaine hydrochloride, which releases hydrochloric acid in the stomach. In studies on volunteers whose stomach acid had been suppressed, two 750-milligram tablets taken on an empty stomach kept the stomach pH below 3 for up to 75 minutes. That window shortens when you eat. One important distinction: betaine hydrochloride is not the same as trimethylglycine, which is also called “betaine” but does not produce any acid.
Apple cider vinegar is a popular alternative. Most varieties contain about 5% acetic acid, and the typical recommendation is 1 to 2 tablespoons diluted in 8 ounces of water, split into two doses per day and taken around mealtimes. Citric acid dissolved in water (150 to 300 milligrams in about 16 ounces, divided into two doses) is another option.
For any of these, the general guidance is to start with a low dose, take it with meals, and gradually increase if needed. Increasing the volume of liquid you drink with meals can also help with digestive symptoms. If you experience burning or discomfort, that’s a sign to reduce the dose or stop.
Restoring Your Skin’s Acid Mantle
Your skin’s outer layer maintains a slightly acidic pH, typically between 4.5 and 5.5. This “acid mantle” acts as a barrier against bacteria, fungi, and environmental irritants. Soap, especially bar soap with a pH of 9 or 10, strips this acidity away. So do harsh cleansers, over-exfoliation, and prolonged water exposure.
The simplest way to lower skin pH is to switch to a cleanser with a pH close to 5. Many gel and foam cleansers marketed as “pH-balanced” fall in this range. Alpha-hydroxy acids (AHAs) like glycolic acid and lactic acid also lower skin pH directly. At the skin’s surface, these acids break down the bonds between dead skin cells, promoting turnover while simultaneously restoring acidity. Their effectiveness depends on concentration, the pH of the product, how long it stays on your skin, and how much free acid is available.
A diluted apple cider vinegar rinse (roughly 1 part vinegar to 3 or 4 parts water) is sometimes used as a toner to bring skin pH down, though it can irritate sensitive skin. After cleansing, applying a product with a mildly acidic pH, whether that’s a toner, serum, or moisturizer, helps the acid mantle recover faster than leaving skin bare.