context: When you look for a probiotic, there are a lot of products to pick from. You'll find many brands with different ingredients, and everything from pills to powders to liquids. Take a few moments to learn how to navigate through the options, and you'll be rewarded with the right probiotic to boost your health. For most people in good health, experts say probiotics won't cause any issues. If you do get side effects, they're usually very mild, like a little more gas than usual. But use caution if you have a serious health condition or your immune system -- your body's defense against germs -- is weak. In those cases, it's best to check with your doctor first to see if they're safe. Also talk to your doctor before giving probiotics to your infant, especially if he's sick. Probiotics are sold as supplements, just like vitamins and herbs. The FDA doesn't check them for safety or health claims made by the maker, the way they would for drugs. That makes it all the more important to go with a brand you can trust. In one study, five of 19 probiotics had lower counts of bacteria than listed on their labels. And in some cases, they had other bacteria besides the ones that were supposed to be in them. Ask your doctor for suggestions. You can also do research on your own to see which brands get high grades. While you're at it, look for studies that back up any claims made by the maker of the probiotic. Scientists give bacteria three names: genus, species, and strain. You'll see something like " Bifidobacterium longum W11," where bifidobacterium is the genus, longum is the species, and W11 is the strain. You can think of it like a first, middle, and last name. You need all three to get it right. This matters because when scientists research how well probiotics work for a health condition, they use very specific types. When you're choosing a probiotic, make sure all three names are the ones you're looking for. Just the same genus and species won't do. That'd be like settling for some random actor named James Earl Cooper when you really wanted to watch a movie with James Earl Jones. This tells you how much bacteria you're getting in each dose. How much you need varies with different types and what you want to treat. There's no general rule to follow. Most doses range from 1 to 10 billion CFUs that you take once or twice a day. If you don't get enough CFUs, you might not get the results you want. But more isn't always better. It could just be a waste of money. To find out what you might need, ask your doctor. On the label, some makers list CFUs "at time of manufacture." But it's important for the CFU count to tell you how much you're getting when you use the probiotic before it expires. If you're not sure what the count tells you, get in touch with the maker. Keep in mind that the CFU listed is usually the total for all probiotic types in the product. If you can find one that lists it for each type, that's even better. It'll tell you about the strains and CFU, but that's not all you need to know. Also look for important info like: Dose. This will tell you how much to take to get results. Check that the CFU in each dose lines up with what research says you need. How to store it. Some probiotics need to go in the fridge. Make sure the place you're buying it from stores it the way it's supposed to. And when you get home, do the same. Heat-dried formulas should be kept in the refrigerator, while freeze-dried ones can handle room temperature. Other ingredients. Make sure everything in the probiotic is safe and there's nothing you're allergic to, like soy or dairy. " Use by" or expiration date. The amount of CFUs may go down as the product gets older. Check that you're not buying something after, or close to, the date on the package. They have a lot of promise, but probiotics aren't going to work for everyone. You have a different diet and different gut bacteria than the next person. Don't stop any medical treatment you're already getting just because you're trying a probiotic. Once you start, give it a month to see if it works for you. If it doesn't, it's probably time to try something else.