5 Supplements to Avoid for Kidney Health, According to Dietitians
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Key Points
Some supplements may strain the kidneys when taken in high doses or excessively.
High doses of vitamin C and vitamin D as well as some herbs may harm the kidneys.
Protein supplements may need to be limited in those with kidney disease.
Your kidneys work around the clock, tirelessly carrying out critical functions that keep your body in balance. From filtering blood and removing waste to balancing minerals, producing red blood cells and even helping control blood pressure, these hardworking organs play a vital role in many aspects of your health.
Since your kidneys are responsible for removing many of the compounds you put into your body—including ingredients found in supplements—they can be vulnerable to overload. That’s why experts recommend taking a closer look at your supplement routine, as some products may unintentionally harm your kidneys, especially for those with kidney disease. We spoke with registered dietitians to share the top supplements to avoid or limit to protect kidney health.
1. High-Dose Vitamin C
High-dose vitamin C may seem like a simple way to support your immune system, but it can create extra work for your kidneys. “A lot of people think vitamin C is harmless because it’s water-soluble, but megadoses can actually become problematic for kidney health—especially in people who already have kidney disease or a history of kidney stones,” says Vanessa Rissetto, M.S., RD, CDN.
She explains that excess vitamin C can be converted into oxalate in the body, and elevated oxalate levels may contribute to calcium oxalate kidney stones—the most common type. As such, she cautions that taking high-dose vitamin C supplements above 1,000 to 2,000 milligrams per day can put unnecessary stress on the kidneys in susceptible individuals.
Instead, most people can meet their vitamin C needs through food without relying on megadose supplements. After all, more doesn’t always equal better when it comes to supplementation.
2. High-Dose Vitamin D
While vitamin D is essential for bone, immune, muscle and nerve health, too much can place strain on your kidneys. “Extremely high doses of vitamin D supplementation can lead to elevated calcium levels in the blood, which may contribute to kidney stones and, in severe cases, kidney damage,” says Rissetto.
Since vitamin D is commonly added to many supplements, Rissetto points out that people who take multiple supplements may end up consuming excessive amounts. The tolerable upper intake level for vitamin D is 4,000 IU per day for adults, unless otherwise recommended by a health care provider.
“For most people, supplementation should be individualized based on lab work rather than assuming higher doses are automatically beneficial,” Rissetto emphasizes.
3. Herbal Supplements with Aristolochic Acid
Not all herbal supplements are as safe as they seem, especially when it comes to kidney health. Several traditional herbal remedies—particularly plants in the Aristolochia genus, such as birthwort fruit (ma dou ling) and aristolochia vine and root (tian xiang teng and qing mu xiang)—naturally contain a harmful compound called aristolochic acid.
“Aristolochic acid is a known kidney toxin and carcinogen—it has been directly linked to cases of kidney failure,” says Melanie Betz, M.S., RD, CSR, FNKF, FAND, a dietitian specializing in kidney stones.
Rissetto adds that some imported herbal supplements may not clearly disclose all ingredients, and supplements are not as tightly regulated as prescription medications. “That’s why I always tell patients that ‘natural’ does not automatically mean safe. If someone has kidney disease—or honestly even if they don’t—they should be very cautious with unverified herbal blends or supplements purchased from questionable sources online.”
4. St. John’s Wort
St. John’s wort is an herbal supplement commonly used to relieve symptoms of depression. Despite its reputation as a natural mood supporter, it can pose a serious risk for those with kidney conditions.
“St. John’s wort should be avoided for many people with CKD [chronic kidney disease] because it can interfere with common medications for kidney patients,” says Betz. “Most notably, tacrolimus and cyclosporine, which are common anti-rejection medications prescribed to people with kidney transplants.” More specifically, it can speed up the body’s breakdown of these medications, lowering their levels in the bloodstream and making them less effective. As such, you should always speak to your health care provider about any supplements you are taking or considering.
5. Supplements High in Protein
For healthy individuals, protein powders are generally considered safe when taken in the appropriate amounts. However, for those with chronic kidney disease who are not on dialysis, consuming more protein than necessary can overburden the kidneys.
Since the kidneys are responsible for filtering protein byproducts from the blood, Betz highlights that excessive protein intake from supplements, bars and powders can contribute to kidney stones and speed up kidney disease progression. Therefore, it’s best to work with a registered dietitian or health care provider to determine the right amount of protein for your individualized needs.
Other Tips for Supporting Kidney Health
Keeping your kidneys healthy goes beyond avoiding certain supplements. It also means building daily habits that can help these two bean-shaped organs function at their best. Both dietitians recommend these tips for supporting kidney health:
Limit Sodium. “Too much salt can increase blood pressure, which is one of the leading causes of kidney disease,” says Betz. For this reason, she recommends limiting your sodium intake to no more than 2,300 mg per day.
Choose Your Protein Sources Wisely. For people with chronic kidney disease, Betz suggests swapping out several servings of animal protein for whole-food plant proteins like beans, nuts, seeds, tofu or edamame. This is because plant proteins may be gentler on the kidneys.
Drink Plenty of Water. “Dehydration can lead to both kidney stones and kidney damage (in extreme circumstances),” warns Betz. She explains that the right amount of water varies from person to person, but a good rule of thumb is to aim for 80 fluid ounces (2.4 liters) per day. “If you have a history of kidney stones, you should be closer to 100 fluid ounces. If you have advanced kidney failure or are on dialysis, you may need to limit fluids. Ask your health care team what is right for you.”
Get Your Labs Checked Regularly. “Kidney disease can progress silently for years without symptoms, so monitoring things like blood pressure, glucose, creatinine and urinary protein matters—especially if you have diabetes, hypertension or a family history of kidney disease,” says Rissetto.
Our Expert Take
Your kidneys work hard to filter out unwanted waste, toxins and byproducts. That constant workload means what you put in your body—including the supplements you take—can either improve or harm your kidney health. Commonly used supplements like vitamin C, vitamin D, St. John’s wort, herbal remedies containing aristolochic acid, and protein powders can overtax the kidneys when taken in excess or without professional guidance.
Along with being cautious of the supplements you take, simple habits like limiting sodium, choosing protein sources wisely and staying hydrated can all support kidney health and ease the workload on these essential organs.
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