Alkaline water is any water with a pH above 7, though most products marketed as “alkaline water” fall in the pH 8 to 9 range. Regular tap water typically sits around pH 7.5, making it very slightly alkaline already. The difference between what comes out of your faucet and what you see in specialty bottles is often just one or two points on the pH scale, but that small gap has generated a large wellness industry.
How the pH Scale Applies to Water
The pH scale runs from 0 (highly acidic) to 14 (highly alkaline), with 7 as neutral. Each whole number represents a tenfold change in acidity or alkalinity, so water at pH 9 is ten times more alkaline than water at pH 8. The U.S. Environmental Protection Agency recommends drinking water stay between pH 6.5 and 8.5, which means most bottled alkaline waters sit right at the upper edge of that guideline.
Water That’s Naturally Alkaline
Some water becomes alkaline without any processing. When rain or snowmelt flows over certain types of rock, it picks up dissolved minerals that raise its pH. Limestone is the most common source: water running through limestone-rich terrain absorbs calcium carbonate, which pushes the pH upward and adds mineral content. Spring water from these regions can emerge naturally alkaline, sometimes at pH 8 or higher, with calcium, magnesium, and bicarbonate dissolved in it.
Geography matters. Areas with granite bedrock produce water with lower alkalinity because granite doesn’t release the same buffering minerals. Even within the same region, though, local conditions like soil treatment or nearby construction can shift things. A pond in a granite-heavy area might still test alkaline if surrounding lawns have been treated with limestone to improve soil quality.
Naturally alkaline spring waters you’ll see in stores (brands like Evian or Fiji, for instance) get their mineral content and pH from the geology where they’re sourced. The mineral profile varies from brand to brand depending on the rock formations the water passed through.
How Artificial Alkaline Water Is Made
Most alkaline water on the market is produced through one of two methods: electrolysis or mineral additives.
Water ionizers, the countertop machines popular in wellness circles, use electrolysis. The device runs direct current through the water, which splits it into two streams separated by a membrane. On one side, hydrogen ions are converted into hydrogen gas, reducing acidity and producing alkaline water. On the other side, the process creates acidic water as a byproduct. The alkaline stream is dispensed for drinking while the acidic water is discarded or used for cleaning.
The simpler method is adding alkaline minerals directly to purified water. Many bottled alkaline waters start as reverse-osmosis filtered water (which is slightly acidic because filtration strips out minerals), then have calcium, magnesium, or potassium bicarbonate added back to raise the pH. This is how most mass-market alkaline bottled waters are produced.
What Happens When You Drink It
Your stomach is intensely acidic, with a resting pH between 1.5 and 3.5. Once alkaline water reaches your stomach, that acid overwhelms the higher pH almost immediately. As Harvard Health Publishing notes, you could temporarily raise your stomach’s pH by drinking large amounts of alkaline water, but the effect wouldn’t last. Your body tightly regulates its internal pH through your lungs, kidneys, and chemical buffering systems, and drinking alkaline water doesn’t meaningfully shift your blood pH.
This is worth understanding because many alkaline water claims rest on the idea that your body becomes “too acidic” and needs correction. In reality, healthy kidneys and lungs keep blood pH locked between 7.35 and 7.45 regardless of what you drink.
Where the Evidence Shows Some Effect
A few narrow areas of research have produced interesting, if limited, results.
A lab study published in the Annals of Otology, Rhinology, and Laryngology found that water at pH 8.8 permanently inactivated pepsin, the enzyme responsible for the tissue damage in acid reflux. Pepsin remains stable and can reactivate at normal pH (7.4), but at pH 8.8, it was irreversibly denatured. This doesn’t mean drinking alkaline water cures reflux, but it suggests a possible supportive role alongside standard treatment for people with throat-related reflux symptoms.
Research on bone health found that bicarbonate-rich alkaline mineral water reduced markers of bone breakdown in healthy premenopausal women, even when their calcium intake was already adequate. The key factor appeared to be the bicarbonate content rather than the pH alone. A calcium-rich acidic water with low bicarbonate didn’t produce the same effect, which suggests the mineral composition matters more than the number on the pH scale.
One hydration study found that highly alkaline water reduced blood viscosity by about 6.3% after exercise, compared to 3.4% for regular water. Thinner blood flows more easily, which could theoretically improve oxygen delivery during recovery. The study was small and involved recreationally active adults, so it’s far from definitive.
Risks of Drinking Too Much
For most people, drinking alkaline water in normal amounts is harmless. The concern arises with excessive consumption or very high pH levels. Pushing your body’s pH balance too far toward the alkaline side can cause a condition called alkalosis, with symptoms including nausea, muscle twitching, hand tremors, tingling in the face or hands, lightheadedness, and confusion. Severe cases can progress to prolonged muscle spasms or even coma, though reaching that point from water alone would be unusual.
A more practical concern is digestive. Your stomach acid exists for good reason: it breaks down protein, kills bacteria in food, and triggers the release of digestive enzymes further down your gut. Regularly flooding your stomach with high-pH water before or during meals could temporarily dilute that acid and slow the early stages of digestion. People who already produce less stomach acid, which becomes more common with age, may want to be especially cautious.
What Actually Matters More Than pH
The mineral content of your water is generally more relevant to health than its pH. Water rich in calcium, magnesium, and bicarbonate delivers measurable nutrients. Water that’s been artificially raised to pH 9 through electrolysis but contains few dissolved minerals offers less obvious benefit. When comparing alkaline waters, checking the mineral analysis on the label tells you more than the pH number alone.
Staying well hydrated with any clean water is the single most evidence-supported thing you can do. The gap between drinking enough regular water and drinking the same amount of alkaline water is, for most health outcomes, far smaller than the gap between being well hydrated and being even mildly dehydrated.