Most tap water in the United States contains fluoride, either added intentionally or present naturally. In 2022, 72.3% of Americans on community water systems, more than 209 million people, had access to fluoridated water. But fluoride levels vary widely depending on whether you’re drinking municipal tap water, well water, or bottled water, and whether you filter it at home.
Fluoride in Tap Water
The U.S. Public Health Service recommends that community water systems add fluoride to a concentration of 0.7 milligrams per liter (mg/L), a level designed to strengthen teeth while minimizing the risk of dental fluorosis (faint white spots on enamel). Most cities and towns that fluoridate their water target this number. You can check whether your local system adds fluoride by searching the CDC’s “My Water’s Fluoride” tool online, which covers most public water systems.
Not every community participates. Some cities, including Portland, Oregon, have voted against fluoridation. If your water comes from a non-fluoridating system, fluoride may still be present at low levels from natural mineral deposits, but typically well below 0.7 mg/L.
Fluoride in Well Water
Private wells pull from groundwater, which picks up fluoride naturally as it flows through rock and soil. According to the U.S. Geological Survey, more than 85% of domestic wells have fluoride levels below the recommended 0.7 mg/L, meaning most well water doesn’t provide enough fluoride to offer dental benefits.
On the other end of the spectrum, about 1.6% of drinking-water wells exceed the EPA’s maximum contaminant level of 4.0 mg/L. That translates to roughly 172,000 people in the lower 48 states drinking well water with fluoride concentrations high enough to pose health concerns. Another 522,000 people have well water above 2.0 mg/L, a level that can cause cosmetic tooth discoloration over time. Concentrations tend to run higher in the western U.S. than in the east. If you rely on a private well, testing is the only way to know your fluoride level, since it isn’t regulated the way municipal water is.
Fluoride in Bottled Water
Bottled water fluoride content depends almost entirely on the brand and source. Most popular brands contain very little. A study published by the Colorado Dental Association measured fluoride in widely available bottled waters and found that Aquafina, Dasani, and Smartwater all contained less than 0.1 parts per million (ppm), essentially negligible. Fiji water came in at 0.3 ppm, closer to but still below the recommended level for dental benefits.
Some bottled water brands do add fluoride deliberately. The FDA caps added fluoride in bottled water at 0.7 mg/L, matching the public health recommendation for tap water. If fluoride has been added, it must appear on the ingredient label. For bottled water with no added fluoride, the FDA allows naturally occurring levels up to 2.4 mg/L depending on regional climate conditions, and up to 1.4 mg/L for imported water.
If you drink mostly bottled water and want fluoride’s dental benefits, look for brands that specifically list fluoride as an added ingredient. Otherwise, assume your bottled water has little to none.
How Filters Affect Fluoride
Standard pitcher filters and faucet-mounted carbon filters do not remove fluoride. Carbon filtration targets chlorine, taste, and odor but leaves dissolved minerals like fluoride largely untouched. If you use a Brita or similar carbon filter, your water’s fluoride content stays roughly the same.
Reverse osmosis (RO) systems do remove fluoride, along with other dissolved solids like lead and nitrates. Distillation also strips fluoride effectively, since fluoride doesn’t evaporate with the water. If you’ve installed an under-sink RO system, your filtered water will have significantly less fluoride than what comes out of the main tap. This is worth knowing if you chose fluoridated municipal water partly for the dental benefit.
Why Fluoride Is Added to Water
Fluoride strengthens teeth through a process that happens at the enamel surface. When bacteria in your mouth produce acid (after you eat sugary or starchy foods), that acid dissolves minerals from tooth enamel. If fluoride is present in your saliva, it gets incorporated into the enamel as it repairs itself, forming a mineral structure that is harder and more acid-resistant than the original. This means teeth exposed to fluoride don’t just recover from acid attacks; they come back slightly tougher each time.
This process works best with consistent, low-level exposure, which is why water fluoridation targets a modest 0.7 mg/L rather than a high dose. The fluoride in drinking water maintains a steady presence in saliva throughout the day.
Fluoride and Infant Formula
Parents who mix powdered or concentrated formula with tap water sometimes wonder about fluoride exposure for babies. The American Academy of Pediatrics recommends primarily using safe fluoridated tap water for formula preparation, with occasional use of non-fluoridated bottled water. The concern is that infants who get fluoride exclusively from reconstituted formula may develop mild dental fluorosis on their developing permanent teeth, which shows up as faint white markings. This is a cosmetic issue, not a health risk, but parents who want to reduce the chance can alternate between fluoridated tap water and low-fluoride bottled water when preparing bottles.
How to Find Out What’s in Your Water
If you’re on a public water system, your utility is required to publish an annual Consumer Confidence Report listing fluoride levels along with other water quality data. You can usually find it on your water provider’s website or request a copy. The CDC’s “My Water’s Fluoride” database also lets you search by state and county.
For private wells, you’ll need to send a sample to a certified lab. State health departments often maintain lists of approved testing labs, and some offer low-cost fluoride testing. Since natural fluoride levels can shift over time as groundwater conditions change, testing every few years is a reasonable approach if your well has historically been near the upper limits.