Most of us won’t go through life without the occasional episode of heartburn or acid reflux. And when acid does sting your throat or burn in your chest, you might find yourself wondering just how strong the stuff is. Read More: Stomachache? Your Gut Bacteria Might Be to Blame To find out, let’s turn to the pH scale, which measures how acidic or alkaline (basic) a solution is. The scale ranges from 0 to 14, with anything hovering around a value of 7 — like most drinking water — considered neutral. A substance with a pH less than that, like vinegar, is acidic; anything higher, like household bleach, is alkaline. Both strongly acidic and strongly alkaline substances can, of course, be corrosive. The pH of stomach acid (also called gastric acid) usually ranges from around 1.5 to 2. The reason it’s so strong is because specialized stomach cells — called parietal cells — actually produce a small amount of hydrochloric acid in your stomach. Iron Stomach Anyone who’s taken a high school chemistry class will be familiar with this strong acid. As your teacher probably warned you, putting hydrochloric acid on human skin is bad: It will immediately begin dissolving tissue.  Mark Derleth, a gastroenterologist and clinical associate professor of medicine at the University of Washington Medical Center, says the acid is produced is in response to both the anticipation of food and the actual ingestion of it. The response is driven by the vagus nerve, as well as hormones like gastrin and histamine. The reason this acid doesn’t corrode your stomach’s lining is because the stomach also produces a protective layer of bicarbonate and mucous. The former substance is alkaline, which neutralizes acids. The corrosive effects of stomach acid can get the upper hand, however — if you’re not careful. Certain types of medications, Derleth says, can inhibit the body’s production of this protective layer, exposing the stomach to possible acid injury. Especially harmful (if overused) are non-steroidal anti-inflammatory drugs or, as you’ll commonly see on medication warning labels, NSAIDs. These include aspirin, ibuprofen, naproxen and more. While these medications are effective at reducing fevers, inflammation and pain, they also put people at risk for ulcers: painful sores that can form on the lining of the stomach, esophagus or small intestine. State of Flux Whenever you consume a meal, the concentration of stomach acid decreases, Derleth says. Then, as that digested food leaves the stomach, the concentration of acid goes back up. Antacids like Tums, which generally utilize calcium carbonate as their main active ingredient, work to neutralize acid in cases of heartburn or acid indigestion. Likewise, medications like famotidine (with brand names like Pepcid) and omeprazole (with brand names like Prilosec) can reduce stomach acid secretion. When it comes to acid reflux, also known as gastroesophageal reflux disease or GERD, symptoms aren’t caused by the overproduction of acid. Instead, they’re due to where that acid ends up — your esophagus and throat. In addition to occasional medication use to ease reflux symptoms, Derleth recommends certain lifestyle changes, such as waiting two to three hours after your last bite of food to go to bed. Elevating the head of your bed can also help, as can losing weight and cutting back on caffeine, alcohol, and nicotine. Read More: If Marijuana Gives You an Upset Stomach, You’re Not Alone Out of the Ordinary Other health conditions can destabilize normal acid concentrations too, Derleth says. These include common chronic stomach infections, like those caused by the Helicobacter pylori bacteria. Zollinger-Ellison syndrome, a rare condition associated with a tumor called a gastrinoma, can also significantly increase the amount of acid in your stomach. Problems may also arise from not having enough acid. Though production often decreases slightly with age, conditions like autoimmune atrophic gastritis can additionally limit acid production and result in upper gastrointestinal symptoms like indigestion. Upper GI symptoms that don’t respond to lifestyle or short-term medication should prompt a visit to a healthcare provider, Derleth says, especially if they’re “red flag” symptoms. These include difficulty swallowing, feeling like food is stuck in your esophagus and consistently feeling full even early on in a meal. So, the next time you reach for a bottle of Tums, consider the science behind the acid bubbling in your belly.