Milk of magnesia has a pH of 10.5, as noted by About.com. Also known by its scientific name magnesium hydroxide, milk of magnesia is an alkaline base used to treat occasional symptoms of constipation, upset stomach, heart burn and indigestion.
WebMD states that milk of magnesia works as an antacid that lowers acid content in the stomach by raising the pH of gastric juices.
One should always seek the advice of a physician before using any medication, and one should report symptoms such as dehydration, diarrhea that becomes persistent, rectal bleeding or severe dizziness. People who display symptoms of appendicitis or kidney disease should consult a pharmacist or physician before using this medication, according to WebMD.