Peek inside a friend’s medicine cabinet and you’ll probably spot a dietary supplement or two. After all, Americans are estimated to spend more than 50 billion dollars on supplements annually. That’s a ton of cash thrown at a broad and sometimes murky category that houses everything from multivitamins and greens powders to electrolytes and ancient herbs—and that notoriously has limited oversight from federal regulatory agencies.

Though supplements give off an *all natural* aura—and can be useful in certain cases—there are real risks involved with blindly popping a pill you heard about on TikTok. Below, six common supplement mistakes I see as a registered dietitian.

What not to do when taking supplements

1. Taking something without confirming whether you need it

Ever heard the phrase: “Test, don’t guess?” The mantra is a friendly reminder that providers need data before they can recommend targeted medical or nutritional interventions.

The same idea applies to supplements. Tons of people come to me taking a vitamin B12 supplement “for energy,” but a B12 supplement won’t do you much good unless your bloodwork indicates that you’re deficient in vitamin B12.

Luckily B12 is a water-soluble vitamin, which means that any excess you consume will be removed from the body through your urine. So unnecessarily supplementing B12 will mostly just result in you pissing away your money. (Sorry, I had to.)

Tons of people pop supplements without an awareness of the dose they’re taking or whether that dosage actually makes any sense.

Taking unnecessary supplements isn’t always low risk, though. Other nutrients, like vitamin D, aren’t automatically escorted out of the body when consumed in excess, so supplementing them without reason—especially at high doses—could lead to dangerously high blood levels over time. And that can have serious consequences: A 2022 case study published in the BMJ: Case Reports found that a man was hospitalized for eight days with extreme symptoms (including constant vomiting, diarrhea, and extreme thirst) after taking extremely high doses of vitamin D supplements.

Another example: Taking a buzzy “hormone balancing” supplement without confirming that you actually have a hormonal imbalance. Using a supplement for estrogen dominance without knowing whether you even have elevated estrogen levels could leave you feeling worse, not better. (The only thing more annoying than a true hot flash is a hot flash you gave yourself.)

I recommend getting clear on why you’re taking a supplement by asking yourself these questions:

  • Do I have a clear and confirmed reason for taking this supplement?
  • Was this supplement recommended or reviewed by my health-care provider?
  • If you’re taking a singular nutrient, like vitamin D or iron, for a deficiency: Have I rechecked my blood levels to see how this supplement has affected them?

Consider getting updated labs done every three to six months to determine whether or not your levels have normalized if you’re taking a supplement to treat a nutrient deficiency.

I’ve had clients in their 30s tell me they’re still taking a supplement their doctor recommended to them at age 17. Most likely, that is no longer necessary.

2. Taking a dose that makes no sense

Would you rather choke down 10 fiber pills every day, or add a spoonful of chia seeds to your breakfast? I ask because swallowing 10 (10!) Metamucil fiber capsules will supply you with four grams of fiber, the same amount you’d get from eating just 1 tablespoon of chia seeds. Not to mention you’ll also get a small amount of calcium and omega-3s from the chia.

This is one of those supplement mistakes I see all the time in my practice. Tons of people pop supplements without an awareness of the dose they’re taking or whether that dosage actually makes any sense. Sometimes it’s comically low, other times it’s frighteningly high.

Once you’ve confirmed that you’d benefit from a certain supplement, talk to your provider about the correct dosage for you. Even compounds that our bodies naturally produce, like melatonin, have upper limits when taken in supplement form.

3. Taking the wrong form of a supplement

Different forms of the same nutrient can have vastly different effects on the body. Take magnesium, for example. Magnesium glycinate supplements may be helpful for nighttime relaxation, while magnesium citrate and magnesium oxide supplements act as laxatives2. Accidentally taking magnesium oxide before spending the night with your new boo will literally be the opposite of relaxing, so make sure you select the right form of a nutrient to achieve your desired results.

The specific form a nutrient comes in can also impact how much of it is absorbed by the body and how likely it is to cause side effects. For instance, iron supplements are notorious for inducing GI distress, but some studies show3 that certain forms of iron, such as ferrous bisglycinate, may be less likely to cause nausea and constipation than others, like ferrous sulfate.

4. Taking supplements that interact with medications

Perhaps the gravest of the supplement mistakes is unknowingly taking something that can interact with your medications. A few examples:

This is why if you’re taking any prescription medication, you should always, always ask your doctor or pharmacist about supplements before trying them.

5. Taking supplements with an excessive ingredient list

I prefer to take a minimalist approach when it comes to supplement formulations. When a brand sells a product that purportedly contains vitamins, minerals, probiotics, prebiotics, algaes, fish oil, broccoli extracts, caffeine, and some 300 other nutrients, I get skeptical. It’s challenging to fit so many high-quality, active ingredients into a single capsule or scoop of powder, so ultra comprehensive formulations give me pause.

Another red flag: Supplements made from proprietary blends that leave consumers in the dark about the exact ingredients and dosages contained within the product. I’m not anti-supplements, I’m just pro-transparency.

6. Doubling up on ingredients

One of the most common supplement mistakes is to unknowingly double or triple up on the same nutrients. This happens often when people are taking multiple products. Taking a hair, skin, and nails supplement that contains biotin, plus a B complex for low energy levels, plus a prenatal all at once will mean you’re getting the same B vitamins from three different sources.

When it comes to supplements, more isn’t always better. Work with a credentialed provider to streamline your routine, and save your hard-earned money.


Well+Good articles reference scientific, reliable, recent, robust studies to back up the information we share. You can trust us along your wellness journey.


  1. Alkundi, Alamin et al. “Vitamin D intoxication and severe hypercalcaemia complicating nutritional supplements misuse.” BMJ case reports vol. 15,7 e250553. 6 Jul. 2022, doi:10.1136/bcr-2022-250553

  2. Mori, Hideki et al. “Magnesium Oxide in Constipation.” Nutrients vol. 13,2 421. 28 Jan. 2021, doi:10.3390/nu13020421.

  3. Fischer, Jordie A J et al. “The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials.” Nutrition reviews vol. 81,8 (2023): 904-920. doi:10.1093/nutrit/nuac106

  4. Wiesner, Agnieszka et al. “Levothyroxine Interactions with Food and Dietary Supplements-A Systematic Review.” Pharmaceuticals (Basel, Switzerland) vol. 14,3 206. 2 Mar. 2021, doi:10.3390/ph14030206


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