In medical speak, sublingual means “under the tongue.” What’s so special about this area of the body? For starters, it’s rich in tiny blood vessels. That’s why a thermometer that is placed under the tongue does a good job of measuring your body temperature. But sublingual refers to more than the placement of your thermometer. Certain natural and prescription medicines can be taken sublingually, too. This allows a tablet to be absorbed directly into the bloodstream. That way, it doesn’t enter the digestive system and get processed by the liver before entering the bloodstream. Doctors often recommend sublingual medicines for patients with digestive problems or liver disease because they don’t bother the stomach, and the liver gets a rest from managing or breaking down medication. Sublingual medicines also are helpful for patients who have difficulty swallowing. Some heart and pain medications and vitamins are available in sublingual form, and a compounding pharmacy can convert some other oral medications and supplements into a sublingual version.

In the world of natural medicine, vitamin B-12 is one of our most common sublingual supplements. Unlike other B vitamins, B-12 requires intrinsic factor, a glycoprotein that is produced in cells lining the stomach and allows this vitamin to be absorbed into your bloodstream through your intestine. As we age, we can make less intrinsic factor. People of any age who have stomach problems such as gastritis or an ulcer also may be deficient in this vitamin protein. If you have low intrinsic factor, odds are that you’re B-12 deficient.

A B-12 deficiency is significant because this vitamin is crucial for healthy brain and nerve function. B-12 works with folic acid (another B vitamin) to make a compound known as SAMe (short for S-adenosylmethionine), which boosts our moods and immunity. A B-12 deficiency can cause poor cognition, depression and fatigue. For people who are deficient in this powerful vitamin, doctors have long given B-12 shots (usually monthly). However, research has shown that daily sublingual B-12 also can be effective in getting this vitamin into your bloodstream. And a daily cherry-flavored B-12 sublingual tablet is much more pleasant than a shot!

The hormone progesterone is most readily absorbed into the bloodstream when it is given in a sublingual form or through a skin lotion. Sublingual administration is the tried-and-true method for delivering homeopathic remedies as well. That’s because these remedies need to be directly absorbed into the bloodstream. So placing two little homeopathic tablets or two drops of a liquid preparation under the tongue (before or after eating) is the most effective way of delivering a homeopathic treatment. Caution: Sublingual medications can irritate mouth sores.

My advice: Ask your doctor if there are any sublingual medications you could take instead of the oral form. Because of how efficiently sublingual medicines are absorbed, they are more potent than oral doses. For this reason, discuss the dose of any sublingual medicine with your doctor—you may be able to take a lower dose and perhaps lower your risk for side effects. Also, because eating and drinking can interfere with absorption of the drug, ask how long you need to wait to eat or drink after taking a sublingual tablet.