Supplements for Kidneys: Should I Take Them?

Trang Tran, PharmD
·22 min read
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A pharmacist's take on supplements used for kidney conditions

Medically reviewed by Suzanne Fisher, RD

The kidneys are two fist-sized, bean-shaped organs located below the rib cage that have the following functions:

  • Remove waste and extra fluid from your body

  • Maintain a healthy balance of water, salts, and minerals (e.g., sodium, calcium, phosphorus, and potassium) in your blood

  • Produce hormones that regulate blood pressure, make red blood cells, and maintain bone health

High blood pressure or diabetes may increase your risk of kidney disease.

Other kidney problems include the following:

Some common supplements used for the kidneys include the following:

This article discusses some of the supplements used for certain kidney problems, their side effects and risks, and some supplements to avoid.



Explainer

In the United States, the Food and Drug Administration (FDA) does not regulate supplements the way it regulates prescription drugs. That means some supplement products may not contain what the label says.

When choosing a supplement, look for third-party tested products and consult a healthcare provider, registered dietitian (RD) or registered dietitian nutritionist (RDN), or pharmacist.



<p>Grace Cary / Getty Images</p> Black female holding pills in the palm of her hand

Grace Cary / Getty Images

Black female holding pills in the palm of her hand

What Supplements Are Used for Kidneys?



Explainer

Supplement use should be individualized and vetted by a healthcare professional, such as an RD or RDN, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.



Calcium

Chronic kidney disease decreases the ability of the kidneys to excrete phosphorus. This can result in increased phosphorus levels in the blood.

In CKD, the kidney production of active vitamin D is also impaired.

Vitamin D is essential for the intestinal absorption of calcium. A vitamin D deficiency also decreases calcium absorption.

The Research

Calcium levels may fluctuate (go up and down) with end-stage CKD. Phosphate binders (medications that prevent phosphorus absorption from food) in calcium supplements seem to address both high and low calcium levels.

In people with stage 5 CKD on dialysis, calcium supplements can also be taken with meals, serving as dietary phosphate binders.

Phosphate binders help reduce the amount of phosphorus available for absorption in the gut. The three calcium-based phosphate binders are as follows:

Dosage

The Kidney Disease Improving Global Outcomes (KDIGO) guidelines do not suggest limits for dietary calcium intake or any maximum level of total intake.

Side Effects

Common side effects of calcium include the following:

Excessive calcium intake can cause the following:

  • Increased calcium levels in the blood

  • Increased calcium levels in the urine

  • Decreased phosphate levels in the blood

  • Heart arrhythmia (irregular heart rate)

Interactions

Calcium supplements can interact with some medications, such as the following:

Food: Absorption of calcium carbonate depends on an acidic environment; it should be taken with food.

Acid-reducing drugs: This class, which includes Prilosec (omeprazole), can decrease the absorption of calcium carbonate.

Please consult with your healthcare provider or pharmacist on the appropriate timing of when to take your calcium supplement and medications.

Precautions

Calcium levels that are too low increase the risk of bone fractures; calcium supplementation can correct low calcium levels.

Even though calcium citrate is more easily absorbed than calcium carbonate, it is not recommended in people with CKD due to the potential for citrate to increase aluminum absorption.

However, with advanced kidney disease, the kidneys can no longer release calcium via the urine. This increases the risk of excessive calcium retention. Caution should be taken with calcium supplementation in this case.

Calcium levels that are too high increase the risk of heart and blood vessel problems.

Additionally, it is suggested that calcium levels that are too high can increase the risk of kidney stones.

N-Acetyl Cysteine (NAC)



Explainer

Many dietary supplement products contain NAC. However, NAC is technically an approved drug for the treatment of Tylenol (acetaminophen) overdose. It is also a mucolytic (mucus-thinning) agent in certain respiratory diseases, per the FDA. However, the FDA is considering changing its stance and may allow for NAC in dietary supplements if no safety issues come up.



Chronic kidney disease is associated with an increased risk of the following:

The Research

N-acetylcysteine, a compound with antioxidant effects, had the following effects among people over 18 years old with CKD based on an analysis of a group of studies:

Further studies examining the effect of NAC supplementation on various causes of CKD and the various stages of CKD are warranted.

More rigorous studies conducted in various populations are needed to confirm the results.

Dosage

Common dosages of NAC include the following:

  • CKD: Dosages ranged from 600 milligrams (mg) twice daily to 1,200 mg twice daily by mouth. Intravenously (within a vein), NAC of 5 grams (g) in 5% glucose solution was given for four hours during a single hemodialysis session. NAC treatment duration of more than one month significantly decreased inflammatory markers compared to the placebo group.

  • Preventing kidney damage caused by contrast dye: Average dosing is 1,200 mg per day on the day before and the day of exposure to contrast.

Side Effects

Common side effects of NAC given by mouth and through the vein include the following:

The sulfur compound in NAC gives it a pungent smell, which resembles rotten eggs. This can contribute to nausea and vomiting after NAC is taken by mouth.

Severe allergic reactions such as the following have been reported after the IV administration of NAC:

In people with asthma, such allergic reactions can be more severe and even fatal. Caution is advised.

Furthermore, chest tightness and bronchoconstriction (narrowing of the airways) have been reported after using NAC.

Interactions

NAC interactions include the following:

Precautions

Precautions for NAC include the following:

  • Allergy: Avoid using NAC if you have a known allergy to it or its ingredients.

  • Pregnancy: Although NAC crosses the placenta, there is no evidence that it harms the fetus. However, NAC should only be used when medically needed.

  • Breastfeeding: The safety of NAC during breastfeeding is unknown. It is advisable to avoid use.

  • Children: NAC is likely safe when taken by mouth at daily doses of 900 to 2,700 mg for up to 12 weeks.

  • Asthma: NAC, if taken by mouth or inhaled, might cause constriction of the airways in people with asthma. If you have asthma, check with your healthcare provider before starting the NAC supplement.

  • Bleeding disorder: NAC might slow blood clotting and, therefore, increase the risk of bruising and bleeding in people with bleeding disorders.

  • Surgery: Since NAC might slow blood clotting and increase the risk of bleeding during and after surgery, it is advisable to stop NAC at least two weeks prior to scheduled surgery. 

B Vitamins

B vitamins impact a wide variety of health conditions. Some medical treatments for CKD can disrupt the body's uptake of certain B vitamins.

For example, dialysis is a type of treatment that helps the body remove excess fluid and waste products from the blood. Dialysis causes a loss of water-soluble vitamins, including the following:

Folate (the natural form of vitamin B9) deficiency increases homocysteine, a type of amino acid associated with heart and blood vessel problems.

The Research

One study showed that taking vitamin B12 (cobalamin) with folate significantly lowered homocysteine levels in people with end-stage renal disease (ESRD) or kidney failure.

High phosphate levels are common in people with ESRD. Niacin (vitamin B3) reduced phosphate levels in people undergoing dialysis. Unlike phosphate binders, such as calcium supplements, niacin does not need to be given with a meal.

Supplementation with folate did not reduce cardiovascular events (heart attack or stroke) in people with CKD. However, one study showed that three months of folic acid supplementation in people with CKD stages 3a and 3b reduced oxidative stress.

Vitamin B6 supplementation in people with normal or high oxalate levels with kidney stones decreased oxalate's excretion into the urine.

Dosage

B vitamin dosages used in clinical trials include the following:

  • Niacin at a dose of 400 to 1,000 mg per day was used in clinical studies to reduce phosphate levels and calcium phosphate levels and also increase high-density lipoprotein (HDL) cholesterol ("good cholesterol") levels in people with CKD stages 3 to 5.

  • The European Society of Clinical Nutrition and Metabolism (ESPEN) guidelines recommend doses of water-soluble vitamin supplements at the recommended dietary allowance (RDA) level (e.g., 1.5 mg or 0.8 mg of thiamine) for people undergoing dialysis.

  • Per the ESPEN guideline, thiamine supplementation at a dose of 5 mg per day is recommended for people with advanced CKD and long-term peritoneal dialysis (done through your abdominal cavity); a dose of 10 mg per day is recommended for people undergoing maintenance hemodialysis.

  • Supplementing with two tablets (one tablet consists of 50 mg of vitamin B1, 10 mg of vitamin B2, 40 mg of vitamin B6, 3 mg of vitamin B9, and 200 mg of vitamin C) after dialysis for three months prevented deficiency of water-soluble vitamins.

  • Vitamin B6 250 mg to 500 mg daily by mouth in people with normal or high oxalate levels decreases oxalate excretion into the urine.

  • The treatment with folic acid (a supplemental form of vitamin B9) 5 mg daily for three months in people with CKD stages 3a and 3b decreased homocysteine levels.

Side effects

Listed below are some of the side effects of various B vitamins.

Niacin

Symptoms of too much niacin include the following:

Flushing can be reduced by taking niacin supplements with food, slowly increasing the dose, or waiting for the body to develop tolerance.

More severe side effects, especially with high doses, may include the following:

Vitamin B6

Long-term daily intake of one to six grams of vitamin B6 (pyridoxine) by mouth for 12 to 40 months has caused:

  • Nerve damage

  • Loss of control of bodily movements

However, the symptoms usually stop when pyridoxine is discontinued. Other symptoms of too much vitamin B6 include the following:

Vitamin B9

The following precautions should be followed with folic acid use:

  • Taking too much folic acid can mask vitamin B12 deficiency.

  • Folic acid corrects anemia caused by vitamin B12 deficiency but not the nerve damage caused by B12 deficiency.

  • As a result, large doses of folic acid can worsen the cognitive symptoms of B12 deficiency.

  • High folic acid intake might increase the risk of colorectal cancer and possibly other cancers in some people.

Precautions

Vitamin B6 deficiency is common in people undergoing hemodialysis and may contribute to anemia.

However, high doses of vitamin B6 may:

B vitamins lower homocysteine levels in the blood. However, high doses of B vitamins in people with advanced CKD or ESRD have been shown to be associated with worsening of left ventricular diastolic dysfunction.  

Iron

When the kidneys are damaged, they produce less erythropoietin, a hormone that signals the bone marrow to make red blood cells. A lower-than-normal red blood cell count can lead to anemia.

Iron is an essential component of hemoglobin, a type of protein in red blood cells that carries oxygen from the lungs to the tissues.

Iron deficiency is also linked to anemia in CKD. Risk factors that contribute to iron deficiency in CKD include the following:

  • Blood loss from the GI tract

  • Repeated blood loss due to retention of blood in dialysis equipment in people on hemodialysis

  • Frequent blood sampling for laboratory testing

  • Blood loss from surgical procedures (e.g., creation of vascular access)

  • Impaired iron absorption due to medication such as gastric acid inhibitors and phosphate binders

  • Reduced iron absorption due to inflammation

The Research

A clinical trial evaluating the effect of iron supplementation on 2,141 people with dialysis-dependent CKD showed that the group with the high-dose iron sucrose supplementation had a lower:

  • Incidence of death

  • Nonfatal cardiovascular (heart) events

  • Hospitalization

  • Erythropoietin stimulating agent (a hormone that stimulates red blood cell production)

  • Transfusion requirements

However, the study set a maximum safety cutoff for the ferritin (a protein that stores iron) levels.

Further studies are needed to clarify the safety of iron supplementation in people with higher starting ferritin levels.

Several guidelines recommend iron supplementation in people with CKD with anemia and iron deficiency.

Moreover, the guidelines recommend intravenous or IV iron supplementation in people with CKD stage 5 on dialysis therapy.

A review of a group of studies indicated that IV iron is also the preferred treatment for people with CKD stages 3 to 5 who are not on dialysis therapy.

Dosage

Below are some of the dosing regimens for various formulations of IV iron for end-stage CKD:

  • Iron sucrose 200 mg, five doses over two weeks

  • Ferumoxytol 510 mg, two doses, three to eight days apart

  • Ferric gluconate in sucrose complex, 250 mg, four doses weekly

  • Ferric carboxymaltose 750 mg, two doses, one week apart

  • Iron isomaltoside 1,000 mg, one dose

  • Iron dextran, 500 to 1,000 mg, frequency varies

Below are some of the dosing regimens for the various oral iron supplements (given by mouth):

  • Ferrous sulfate 325 mg (65 mg of elemental iron per tablet), one tablet, one to three times per day

  • Ferrous gluconate 325 mg (38 mg of elemental iron per tablet), one tablet, one to three times per day

  • Ferrous fumarate 325 mg (106 mg of elemental iron per tablet), one tablet, one to three times per day

  • Ferric maltol 30 mg (30 mg of elemental iron per tablet), one tablet, twice per day

  • Ferric citrate 1,000 mg (210 mg of elemental iron per tablet), one to two tablets, three times per day

Side Effects

Some of the side effects of iron supplements when taken by mouth include the following:

Taking iron supplements with food may reduce stomach upset.

Severe allergic reactions, such as anaphylaxis and respiratory arrest, have been associated with certain older formulations of IV iron dextran supplements.

Less severe hypersensitivity reactions associated with IV iron include dizziness and hypotension (low blood pressure).

Interactions

The following include iron interactions:

  • Levodopa: Iron supplements can decrease the absorption of levodopa (contained in brand-name Sinemet) and thus decrease its efficacy in treating Parkinson's disease.

  • Levothyroxine: Synthroid (levothyroxine) is a thyroid hormone replacement therapy used to treat an underactive thyroid. Taking iron supplements with levothyroxine can decrease levothyroxine's effectiveness.

  • Proton pump inhibitors (PPIs): Acid-reducing drugs, such as Prilosec (omeprazole) and Prevacid (lansoprazole), can decrease the absorption and thus the efficacy of iron supplements.

  • Certain antibiotics: Iron supplements can decrease the efficacy of certain antibiotics, such as Vibramycin (doxycycline) and Cipro (ciprofloxacin).

  • Bisphosphonates: Bisphosphonates are a class of medications used to treat osteoporosis (weak and brittle bones). Taking iron supplements with bisphosphonate drugs, such as Fosamax (alendronate), may decrease the absorption and efficacy of such medication.

  • Cholesterol-lowering medications: Cholesterol-lowering medications like Questran (cholestyramine) and Colestid (colestipol) may interfere with iron absorption.

Please consult your pharmacist about taking iron supplements appropriately if you take any of the above medications.

Precautions

The following precautions are advised with iron use:

  • Severe adverse reactions: Any IV iron may be associated with severe reactions. After IV iron is given, it is advised that people be monitored for 60 minutes for serious reactions, including anaphylaxis (severe allergic reaction), low blood pressure, and respiratory arrest (stopping breathing).

  • Infection: IV iron should not be given during an active infection.

  • Low blood phosphate levels: Certain formulations of IV iron, such as ferric carboxymaltose, have been shown to lower phosphate levels in the blood. Vitamin D deficiency, common in people with CKD, can increase the risk of low phosphate levels.

  • Children: Accidental overdose of iron-containing products can be fatal in children—store iron supplements in a safe, preferably locked, location.

Vitamin D

Vitamin D deficiency is common in people with CKD due to the following:

  • Poor nutrition

  • Limited sun exposure

  • Reduced ability of the kidney to convert vitamin D into its active form

Vitamin D supplementation is needed to increase calcium and decrease parathyroid hormone (PTH) levels in people with CKD.

Dosage

Both vitamin D3 (cholecalciferol) and D2 (ergocalciferol) have been used in studies looking at people with CKD stages 3 and 4.

Doses ranged from 2,000 to 4,000 international units (IU) by mouth daily or 40,000 to 50,000 IU by mouth weekly. The therapy ranged from one to 12 months.

Side Effects

Excessive amounts of vitamin D can cause increased calcium levels in the blood and urine. Symptoms of too much calcium include the following:

  • Nausea

  • Vomiting

  • Muscle weakness

  • Mood disturbances

  • Pain

  • Loss of appetite

  • Dehydration

  • Frequent urination

  • Excessive thirst

  • Kidney stones

More serious side effects include the following:

  • Kidney failure

  • Hardening of soft tissues and blood vessels

  • Irregular heart rate

Interactions

Interactions with the following have been reported with vitamin D:

  • Orlistat: Alli (orlistat), a drug used in conjunction with a reduced-fat diet for weight loss, can reduce the absorption of fat-soluble vitamins, including vitamin D.

  • Statins: Statins are a class of drugs that lower cholesterol. Since vitamin D is derived from cholesterol, statin may reduce vitamin D production. High intake of vitamin D might reduce the effects of statins, such as Lipitor (atorvastatin), Mevacor (lovastatin), and Zocor (simvastatin).

  • Steroids: Corticosteroid medications, such as Deltasone (prednisone), can decrease vitamin D metabolism and increase the risk of vitamin D deficiency.

  • Thiazide diuretics: Thiazide diuretics, such as Microzide (hydrochlorothiazide), are water pills that help reduce fluid buildup in the body and are used to treat high blood pressure. Because thiazide diuretics can increase calcium levels, combining such medications with vitamin D (which increases intestinal absorption of calcium) might cause calcium levels to rise too high.

Precautions

Vitamin D can correct low calcium levels. However, it can also increase phosphorus absorption from the gut. Therefore, it's best to avoid vitamin D supplementation with CKD until phosphorus levels are within normal range.

In the setting of CKD, checking the levels of calcium, phosphorus, and PTH with vitamin D treatment is generally recommended. 



Explainer

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.



Foods for Kidney Health

The following foods are used to manage or prevent kidney disease or kidney stones.



Explainer

Determining the best foods for managing your kidney condition can be overwhelming at times. Your healthcare provider may refer you to a renal dietitian (a dietitian specializing in conditions of the kidneys) for guidance.



Foods for Kidney Disease

Foods and dietary patterns for chronic kidney disease include the following:

  • Lower sodium intake

  • Appropriate amount of protein intake

  • Omega-3 fatty acids (e.g., nuts and fish)

  • Lower phosphorus and potassium intake

Foods lower in phosphorus

Foods higher in phosphorus

Fresh fruits and vegetables

Meat, poultry, fish

Egg whites

Egg yolks

Rice milk (not enriched)

Dairy foods

Home-brewed iced tea

Beans, lentils, nuts

Some bottled iced tea

Oat milk

Foods lower in potassium (200 mg or less per serving)

Foods higher in potassium (more than 200 mg per serving)

Apples

Bananas

Peaches

Oranges

Carrots

Tomatoes

Green beans

Beans

Potatoes

Foods for Kidney Stones

The following may decrease the risk of kidney stone formation or manage symptoms:

  • Dietary citrate derived from citrus fruits

  • A diet consisting of a higher content of potassium, magnesium, and citrate

  • Adequate intake of clean water

  • Lower sodium intake

  • Consuming a low protein-low sodium diet with a calcium content of at least 1 gram per day (e.g., 1,200 mg/day)

  • Eating calcium and oxalate-rich foods (e.g., spinach, rhubarb, rice bran, beets, almonds, cocoa powder, etc.) together

  • Dietary fiber

Supplements to Avoid or Use with Caution

The following supplements should be avoided or used with caution in people with kidney conditions.



Explainer

In general, unless under advised by your healthcare provider, herbal and nutritional supplements should be avoided if you have CKD or are on dialysis. This is due to the increased risk of side effects, herb-drug interactions, and worsening of kidney disease.



Creatine

Creatine is used to increase athletic performance and muscle mass. Although most of the studies indicate that creatine supplementation does not cause kidney damage in young adults and people with CKD, some anecdotal evidence suggests otherwise. Therefore, caution should still be taken.

Vitamins A, E, and K

Vitamin A supplements are not recommended in people with CKD who are on dialysis due to the risk of toxicity. Vitamins A, E, and K are fat-soluble and, therefore, are more likely to build up in the body and increase the risk of toxicity.

Phosphorus-Containing Supplements

In CKD, the body can have trouble getting rid of phosphorus, so phosphorus levels in the body tend to increase. Therefore, phosphorus-containing supplements should be limited or avoided in CKD.

Some herbal supplements that have phosphorus include the following:

Potassium-Containing Supplements

Potassium-containing supplements should be limited or avoided in CKD. Some herbal supplements that have potassium include the following:

Herbal Supplements That Act Like Diuretics

Supplements that act like a diuretic or water pill may cause kidney damage. These include, but aren't limited to, the following:

  • Bucha leaves

  • Juniper berries

  • Uva ursi

  • Parsley

Other Herbal Supplements

Certain supplements, such as the following, may be risky for people with kidney disease, those who have had a kidney transplant, or those who are on dialysis:

People at risk of kidney stones should not exceed an intake of 500 mg of vitamin C by mouth per day.

Always speak with your healthcare provider before taking any herbal or nutritional supplements.



Explainer

Some herbal supplements can be contaminated with the following substances harmful to the kidneys and more:

  • Aristolochic acid

  • Heavy metals (cadmium, mercury, and lead)

Chocolate and hot cocoa have also been found to be contaminated with cadmium.



Summary

Given the complexity of kidney problems, the potential risks and benefits of kidney-supporting supplements should be weighed on a case-by-case basis. It is important to ensure that supplements complement the kidney problems and not worsen them.

Always be sure to consult with your healthcare provider and RD before starting any supplements or making any changes to your diet if you have kidney problems or are on dialysis.

Frequently Asked Questions

What supplements are bad for kidneys?

Caution should be taken with the following supplements if you have kidney problems:

Some dietary supplements are contaminated with heavy metals that may damage the kidneys.

What supplements are good for kidneys?

  • Calcium: Due to impaired vitamin D production in the case of chronic kidney disease, calcium absorption is decreased. Adequate calcium intake is important to maintain bone health. However, too much calcium can cause heart and blood vessel problems.

  • N-acetyl cysteine: NAC is an antioxidant that is used off-label to prevent kidney damage caused by contrast dyes.

  • B complex: Water-soluble vitamins, such as B vitamins, are lost during dialysis (a process that helps the body remove excess fluids and waste products from the blood). However, high doses of B vitamins have been shown to worsen left ventricular diastolic dysfunction (stiffening of heart chambers) in people with CKD or end-stage renal disease (ESRD).

  • Iron: Iron deficiency is linked to CKD with anemia, and therefore, iron supplementation is generally recommended. However, iron therapy should be avoided during an active infection since bacteria depend on iron for their growth.

  • Vitamin D: As a result of impaired kidney function, the kidney is unable to convert vitamin D into its active form. Vitamin D supplementation is needed to aid calcium absorption and decrease parathyroid hormone (PTH) levels in people with CKD. However, vitamin D can increase phosphorus absorption in the gut, thereby compounding the problem of high phosphorus levels in people with CKD.

  • Potassium citrate: Prescription potassium citrate is used to manage kidney stones. Potassium supplements interact with prescription and over-the-counter drugs. They should not be used in certain medical conditions.

Is iron supplement bad for kidneys?

Several clinical practice guidelines recommend iron supplementation given by IV in people with CKD with anemia and iron deficiency on dialysis therapy.

A review of a collection of studies suggested that IV iron is the preferred treatment for people with CKD who are not on dialysis therapy.

Is collagen supplement safe for kidney disease?

Hydroxyproline, one of the amino acids contained in collagen supplements, is broken down into oxalate and increased oxalate levels in the urine. When oxalate, a natural compound found in plants, binds to calcium in the urine, calcium-oxalate stone forms in the kidneys.

Kidney stones increase the risk of CKD.

Therefore, collagen supplements should be avoided if you have kidney stones or disease.

One study suggested that the build-up of collagen in the body sped up the progression of renal fibrosis (scarring of the kidney tissues) and vascular calcification (hardening of the blood vessels).

Read the original article on Verywell Health.