Are you just peeing out your vitamins?

When it comes to nourishing your body, you can do everything right—eat the rainbow, take your vitamins—but end up, basically, peeing out all of the good stuff. That’s because bioavailability, or how well the body is able to absorb nutrients, matters. A lot.

“If you’re not taking supplements or having certain foods in the forms they need to be consumed in, you’re really wasting your time,” says nutrition expert Brooke Alpert, MS, RD, CDN, who represents Nature’s Origin, the GMO-free vitamin and supplement brand.

“Bioavailability is very important in a couple of ways,” echoes functional medicine physician Susan Blum, MD. “There are some specific nutrients where it’s much more of an issue than others.”

Here are their tips to avoid flushing your hard work—and dollars—down the toilet.

1. Consider chelation. Minerals like zinc, magnesium, and iron—which the body uses for everything from making hormones to regulating your heartbeat—are inorganic compounds, Dr. Blum explains, meaning there are limits to how well your body can absorb and utilize them. Chelated minerals are attached to an amino acid, which is really the “gold standard” for absorption, she says.

2. Look for activated Bs. The B vitamins, especially B12, have become incredibly popular. But some people have trouble “activating” B vitamins, like folate, B6, and B12 in order to make them useful in the body, which is why many manufacturers offer them in their activated form. “When you’re talking about activation of B12 and folate, you’re talking about the methyl form, so methyl folate and methyl B12,” Blum says. “For B6, you want something called ‘P5P.’”

3. Split the dosage. Alpert regularly sees women in her practice who take a calcium supplement—something she’s all for—but they pop 1,000 mg all at once. “The body can’t absorb more than 500 mg at a time,” she says. Split the dose instead. Ditto for vitamin C, which many people “pound” at the first sign of a cold, even though the body simply stops absorbing it once it’s no longer deficient. “You’re really just getting expensive urine,” Alpert warns.

4. What you take it with matters. This is true for both supplements and actual food. Alpert has plenty of “fat-phobic” clients who are reluctant to add avocado, nuts, or olive oil to their salads, even though they facilitate the absorption of fat soluble vitamins—think A, B, D and K—in all those veggies. Iron’s another key one—if you take your supplement with coffee or tea, it’ll seriously hamper absorption. Take it with a little citrus fruit instead.

5. Look for a really wordy label. Shopping for vitamins and supplements is one of the few places where the keep-it-simple maxim doesn’t apply. “If it’s just listing Vitamin A, Vitamin D, Vitamin E…and doesn’t tell you what form it’s in, it’s not a good vitamin,” Dr. Blum says. It’s better to have more information about bioavailability (and ask for clarification) than to have too little.

6. When in doubt, choose one with a USP seal. Your vitamin won’t do you any good if it doesn’t break down in the body in the proper way, which generally means that it needs to rupture within 15 minutes if it’s a gel pill, and disintegrate within 45 if it’s a tablet. The USP seal lets you know it meets those standards—and others, Alpert says.