The supplement industry is unbelievably massive. It was a $69.3 billion dollar behemoth in 2024 and it’s only gotten bigger since. The problem is, a lot of the products on the shelves in the supplement aisle are more marketing than medicine.
It doesn’t make a lot of sense, but many of the products are not evaluated by the FDA. Even though they make many claims that sound like they are either medical in nature (and can help cure or alleviate symptoms.)
Or others are backed by pseudo-science that has very thin or zero data to back up its claims. But people still treat supplements like medicine but they don’t actually contact their doctor before adding them to their intake regimen.
So hopefully we can help clear up a few things and make sure you don’t make the same mistakes many others have made.
And when we say taking the wrong supplements or mixing them with things can have negative impacts on your health, some of them can be very serious. To name just a few examples, there have been stories of people bleeding during routine surgery because they didn’t tell the surgeon that they took a turmeric capsule, pregnancy issues happened when St. John’s Wort was combined with a contraceptive hormone therapy pill, as well as Vitamin D hypercalcemia from megadoses of Vitamin D.
And before we jump in we don’t want you to think that this means all supplements are bad. In fact, many are great. It’s just that you have to know the right ways to take them (assuming you’re safe to take them and don’t have any conflicting issues.)
Just a few things to think about before blindly adding supplements to your routine are interactions with your current medications (or supplements), safe threshold levels and quality control issues. And as always, ask your doctor or pharmacist before taking any new supplement.
What the FDA actually checks (and what it doesn’t)
The supplement world is basically the honor system. The FDA doesn’t approve supplements before they hit the market. Manufacturers self-attest what is in their products and the FDA typically only acts after there’s been adverse events (ie: when it’s too late.)
But as with any honor system, it’s only as good as the people who actually honor it. And obviously there can be some bad actors in the space (and to be fair, some of those bad actors may not even know they are bad actors.)
Here’s what to look for on any label: USP Verified, NSF Certified, or ConsumerLab Approved.
“Under DSHEA, FDA does not have the authority to approve dietary supplements before they are marketed. […] FDA generally does not approve dietary supplement claims or other labeling before use.”
The ten supplements that follow are common, easy to buy, and where the gap between “what the label says” and “what the body actually does” tends to bite hardest.
10. Fish oil (omega-3)
Here’s the thing about fish oil: it actually works! It’s great for heart health and triglyceride management. The problem with it is that a lot of the fish oil capsules on the shelves are rancid.
Gross, right? In one study that tested 32 supplements a whopping 83% of them were rancid. That’s a lot! And to make it worse, only three of the 32 that were tested actually had the amount of omega-3 it claimed to have.
Here’s what you can do: Buy IFOS-certified or USP-verified only capsules. Make sure it says that on the label. And then open one up and see if it smells rancid. If it does take it back. We also always recommend asking your doctor which capsules he or she takes.
“Many people continue to take fish oil supplements to prevent heart disease. However, the fish oil medication we tested in the STRENGTH trial was not effective for that purpose.”
Make sure to purchase fish oil that is IFOS certified or USP verified, which indicates the product is clean and free of contaminants like mercury. Before consuming fish oil, it’s also a good idea to crack one of the capsules open. If it gives off a really strong fishy smell, don’t take it. That means it’s gone bad (aka, it’s oxidized). Oxidized fish oil is ineffective and potentially harmful.
Finally, talk to your cardiologist before taking fish oil if you are on a blood thinner such as warfarin, apixaban, or aspirin, because fish oil combined with a blood thinner can increase your risk of bleeding. Fish oil in high doses of more than 2 g/day can also increase your risk of bleeding.
9. Ashwagandha
Ashwagandha sales tripled between 2019 and 2024 on the strength of stress and sleep claims. The caveat: it’s an immune-modulating adaptogen. The Memorial Sloan Kettering monograph flags ashwagandha as contraindicated in autoimmune conditions — Hashimoto’s, lupus, rheumatoid arthritis, multiple sclerosis — because it can amplify immune activity in the wrong direction.
Ashwagandha interacts with a couple of common prescriptions. Thyroid medications: Ashwagandha slightly increases thyroid hormone production, potentially making thyroid levels difficult to control, particularly for those taking levothyroxine. Check with your pharmacist before you start it.
“There have been more than 70 reports in the literature of ashwagandha causing liver injury — anything from a mild injury to a prolonged course of jaundice, or even cases of acute liver failure that require a liver transplant.”
Before taking: Get a TSH if you’ve never had one, and skip ashwagandha entirely if you have any autoimmune diagnosis or take thyroid medication.
8. Ginkgo biloba
Ginkgo is commonly used and sold as a supplement for memory, but it has a strong blood-thinning effect. Its ability to thin your blood, known as anticoagulant and antiplatelet effects, interferes with your body’s ability to make normal platelet clumps (aggregation). Case reports have been published about people who have experienced spontaneous bleeding, including bleeding in the head, while taking ginkgo. The risk of bleeding is increased when it is taken with aspirin, warfarin, other anti-inflammatory drugs such as NSAIDs, and even fish oil. The National Center for Complementary and Integrative Health, a research arm of the NIH, recommends avoiding ginkgo for at least 2 weeks before surgery.
If you’re using ginkgo, stop using it at least 2 weeks before any scheduled surgery, dental work, or other invasive procedure, such as a scope, and let your doctors know that you take it. Also, it’s important that you always let prescribers know if you’re taking ginkgo.
“Talk with your healthcare provider if you’re taking blood thinners such as warfarin. Ginkgo may increase your risk of bleeding.”
7. Calcium
The evidence points at calcium supplements rather than calcium from food. In 2010, Mark Bolland conducted a meta-analysis (combination) of 15 randomized trials and found taking calcium supplements not combined with vitamin D was associated with a 27 percent higher relative risk of heart attack. The confidence interval on that was wide, so treat it as a signal worth knowing rather than a settled number.
Try to get most of the 1,000 to 1,200 mg of calcium an adult needs each day from foods like leafy greens, sardines, yogurt, and fortified plant-based milks. If you take calcium, take it with vitamin D3 (1,000-2,000 IU) and make sure you’re taking it at least 2 hours away from any iron supplementation.
“Calcium supplements (without coadministered vitamin D) are associated with an increased risk of myocardial infarction.”
6. Vitamin A (retinol or beta-carotene)
Vitamin A is fat-soluble, which means your body can’t get rid of the excess, so it builds up. Pregnant women should be especially wary of vitamin A taken in the form of retinol. More than 10,000 IU per day is known to cause birth defects during pregnancy, so pregnant women are advised to avoid vitamin A in this form altogether and check that their prenatal multivitamin only includes vitamin A in the form of beta-carotene. Beta-carotene supplements are off the table for current or recent smokers, after a study called CARET, randomized and published in the New England Journal of Medicine, was stopped early when it became clear that taking beta-carotene increased lung cancer rates by 28 percent. Check labels carefully and talk to your doctor before starting a new vitamin, especially if you’re pregnant or have recently quit smoking.
“The trial was ended prematurely after a mean of 4 years, partly because the supplements were unexpectedly found to have increased lung cancer risk by 28% and death from lung cancer by 46%.”
5. Vitamin D
More is not necessarily better. While megadosing vitamin D has become a wellness trend, studies show taking too much vitamin D over time can lead to elevated blood calcium (hypercalcemia) and can increase the risk of kidney stones. According to a review in the New England Journal of Medicine by Michael Holick, toxicity has been reported with chronic daily intakes of more than 10,000 IU. Other case series have shown toxicity at lower intakes over time because people react differently to supplementation.
If you’re considering megadosing vitamin D, have your 25-hydroxyvitamin D levels checked first. For most people, 1,000 to 2,000 IU/day is sufficient. These numbers assume you’re getting some of your daily intake through dietary sources. If you’re taking more than 4,000 IU/day on a regular basis, consider re-testing your levels every 6 months to avoid elevated vitamin D and possible complications.
“Healthy populations who may benefit from higher dose vitamin D supplements are those 75 and older, pregnant people, adults with prediabetes, and children and adolescents 18 and younger, but we do not recommend routine testing for vitamin D levels in any of these groups.”
4. Iron
Iron deficiency anemia is one of the most common nutritional deficiencies seen in women. Inadvertently taking iron without knowing if you are deficient is one of the main reasons for iron overload. Roughly 1 in 200 Americans of Northern European descent have hereditary hemochromatosis, the most common genetic disorder in that population. Supplemental iron speeds liver damage in people with hemochromatosis.
Only take iron if a test has shown you’re deficient. Always get a ferritin test and CBC (complete blood count) to make sure you are deficient in iron before starting to take it. Take iron on an empty stomach with vitamin C to enhance absorption. Wait at least 2 hours between taking iron and thyroid medications, coffee, and dairy as they compete with iron for absorption.
“Older adults should not take iron supplements for iron-deficiency anemia unless instructed by their physicians.”
3. St. John’s Wort
St. John’s wort is a strong inducer of a liver enzyme called CYP3A4 that metabolizes about half of all prescription drugs. Induction of CYP3A4 leads to increased metabolism of any drug that utilizes this pathway and thus these drugs can be rendered less effective or ineffective.
Examples of prescription drugs that can be impacted by St. John’s wort include the combined oral contraceptive, with reported cases of breakthrough bleeding and unintended pregnancy, warfarin, cyclosporine and other immunosuppressant drugs, HIV protease inhibitors, and most antidepressants in the SSRI and SNRI categories. Use of St. John’s wort with an SSRI or SNRI can result in a condition called serotonin syndrome which is a medical emergency.
Anyone taking a prescription medication of any kind should have a pharmacist screen for interactions before starting it. Also, since it can lead to failure of combined oral contraception, St. John’s wort is not recommended for use in women who do not have another form of birth control to use as backup.
“Taking St. John’s wort can weaken many prescription medicines, such as: Antidepressants […] Birth control pills […] Warfarin, an anticoagulant (blood thinner).”
2. Melatonin
Unlike in the US, melatonin is prescription-only in most of Europe and Australia. The amount of melatonin in sleep aid supplements varies significantly. A 2023 research letter in JAMA found melatonin in commercial gummy brands ranged from 74 percent to 347 percent of what’s stated on the label and some products had additional, unlisted ingredients. Although melatonin is effective to promote sleep onset at a dose of 0.3 to 0.5 mg, most over-the-counter melatonin comes in 3, 5 or 10 mg strengths. Research shows that adolescents who take higher doses of melatonin for extended periods of time have a decrease in their bodies’ melatonin production, which can be concerning during a stage of development.
Take it at the lowest dose (0.5 mg). Take it 30 to 60 minutes before you actually intend to fall asleep. Avoid taking it on a daily basis without a clinician’s advice. Talk to your pediatrician before giving melatonin to your child.
“Twenty-two of 25 products (88%) were inaccurately labeled, and only 3 products (12%) contained a quantity of melatonin that was within ±10% of the declared quantity.”
1. Turmeric / curcumin
Turmeric is one of the most recommended anti-inflammatory supplements in wellness. It’s important to be aware of turmeric and its active ingredient, curcumin’s side effects before getting any kind of surgery. Studies have shown curcumin has antiplatelet and anticoagulant effects that are sometimes comparable to those of low-dose aspirin. Adverse bleeding events have been reported in studies with warfarin use as well as surgery. A review in The American Journal of Medicine (2020) revealed increased INR levels in patients taking warfarin who added high-dose curcumin without telling anyone.
Curcumin may increase levels of some drugs by inhibiting two common liver enzymes, CYP3A4 and CYP2C9, used to break down medications. Curcumin also stimulates bile production. That can be a problem for anyone with gallstones or a blocked bile duct.
Keep in mind that ½-1 tsp of turmeric as a spice is not the same as a curcumin extract of 500-1,000 mg. Stop taking turmeric at least 2 weeks before surgery and dental procedures.
“Turmeric appears to have become the most common cause of clinically apparent, herbal-related liver injury in the United States.”
The 10 supplements at a glance
The three certifications worth looking for
One of the best ways to find a high-quality supplement is to look for products that are tested by a third-party for safety and ingredient quality. Three reliable third-party testing marks to look for are USP, NSF, and ConsumerLab. Since the FDA does not pre-screen dietary supplements, these seals indicate that a product has voluntarily been tested to ensure that it is free of contaminants and contains only the ingredients that are listed on the label. Note though that while a third party can certify that a product contains what it’s supposed to without any harmful contaminants, this is not indicative that the product will treat, cure, or help with anything.
If you decide to take any of these: third-party-tested picks
For readers who’ve weighed the cautions above and decided to proceed, the brands below carry independent verification (USP, NSF, IFOS, or NPA seals) and use the forms most strongly supported in clinical research. None of these recommendations replaces a pharmacist consult — but they’re the products worth narrowing the search to.
- Turmeric / curcumin: Look for Meriva-SF or BCM-95, or curcumin paired with piperine for absorption. Thorne Meriva-SF is one of the most-studied phytosomal forms; curcumin with BioPerine is a more accessible price point.
- Melatonin: Nature Made Melatonin (USP Verified) is widely available in 1 mg, 3 mg, and 5 mg doses — start with 1 mg. For the lower clinically effective range, Pure Encapsulations Melatonin 0.5 mg hits the dose most sleep researchers prefer.
- St. John’s Wort: No brand recommendation. The interaction risk doesn’t disappear with a better product. Anyone on any prescription medication should consult a pharmacist before any St. John’s Wort use, regardless of source.
- Iron: Ferrous bisglycinate is gentler on the stomach than ferrous sulfate. MegaFood Blood Builder pairs gentle iron with vitamin C and folate; Pure Encapsulations Iron-C is a clean clinical option.
- Vitamin D: Look for D3 (cholecalciferol) paired with K2 (menaquinone-7) for proper bone targeting. Thorne Vitamin D + K2 Liquid delivers both in a fat base. Nature Made D3 2000 IU (USP Verified) is a solid drugstore option.
- Vitamin A: No standalone supplement recommendation. Whole-food beta-carotene (carrots, sweet potatoes, leafy greens) is the safer route. Pregnant women should get vitamin A only through a prenatal multivitamin formulated for pregnancy — never as standalone retinol.
- Calcium: Calcium citrate is more bioavailable than carbonate and doesn’t require stomach acid. Citracal Calcium Citrate + D3 is the widely available drugstore option; Pure Encapsulations Calcium Citrate is the clean clinical pick.
- Ginkgo biloba: EGb 761 is the standardized extract used in the bulk of clinical trials. Nature’s Way Ginkgold uses this form. Stop two weeks before any surgery, regardless of brand.
- Ashwagandha: KSM-66 and Sensoril are the two most-studied standardized extracts. Nature Made Ashwagandha (USP Verified) uses KSM-66. Skip entirely if you have any autoimmune condition or take thyroid medication.
- Fish oil (omega-3): IFOS five-star certification is the strictest independent purity and freshness standard. Nordic Naturals Ultimate Omega and Carlson Maximum Omega 2000 both carry it. Refrigerate after opening.
“If it’s USP Verified, consumers can trust that what’s on the label is what’s in the bottle.”
The pharmacist conversation worth having
Most chain pharmacies offer medication therapy management consultations for free. You bring in your full list of prescription meds that you take on a regular basis (including specific doses), plus any over-the-counter drugs or supplements, and the pharmacist reviews the list to make sure there are no negative interactions between medications or supplements.
Drug labels are helpful, but they’re generalized. Your pharmacist has been trained to consider your overall health and medication regimen, and can advise you accordingly. Ten minutes with your pharmacist is the cheapest insurance policy to make sure there are no drug-drug or drug-supplement interactions before heading into a procedure, picking up a new medication, or starting a new vitamin/supplement regimen.
Supplements aren’t risky in the abstract. They’re risky in the specific case. A supplement isn’t automatically safe just because it’s natural.
“The pharmacist plays a key role in ensuring that the balance of OTC use tips toward benefit rather than risk.”
This article is for general information only and is not a substitute for medical or pharmacy advice. Talk to a qualified clinician before starting, stopping, or changing any supplement.
Want an age-specific approach instead? Here’s our rundown of the supplements every woman should take in her 50s.
Joseph has been writing and editing for a wide variety of publications over the last decade. He loves covering news in the health and wellness space and has written extensively about all aspects of wellness for a wide range of publications.
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