Yes, high doses of vitamin C can negatively affect the kidneys, primarily by increasing the risk of kidney stones (especially calcium oxalate stones) and, in rare cases, leading to acute kidney injury or oxalate nephropathy, particularly in individuals with pre-existing kidney issues or G6PD deficiency. While essential in moderation, excessive supplemental vitamin C gets converted partly to oxalate, which can crystallize in the kidneys, making it important for those with a history of stones to limit intake.
After about 1,000mg of vitamin C, your body will probably be unable to absorb any more and the excess will simply be flushed out in urine. More importantly, consuming too much vitamin C can have negative outcomes like diarrhea and an increased likelihood of kidney-stone formation.
Here's a breakdown of the six most common supplements people with CKD may need to support kidney health.
The fat soluble vitamins (A, D, E and K) are more likely to build up in your body, so these are avoided unless prescribed by your kidney doctor. Vitamin A is especially a concern, as toxic levels may occur with daily supplements. Vitamin C supplements are recommended in a 60 to 100 mg dose.
To strengthen your kidneys, focus on a healthy lifestyle: stay hydrated with water, eat a balanced diet low in salt and processed foods, exercise regularly, avoid smoking and excessive alcohol, manage blood pressure and sugar, limit over-the-counter pain relievers (like NSAIDs), and maintain a healthy weight to support overall kidney function.
Vitamin C has low toxicity and is not believed to cause serious adverse effects at high intakes [8]. The most common complaints are diarrhea, nausea, abdominal cramps, and other gastrointestinal disturbances due to the osmotic effect of unabsorbed vitamin C in the gastrointestinal tract [4,8].
Diabetes and high blood pressure are the top culprits damaging kidneys most, as they harm the delicate filtering blood vessels, leading to chronic kidney disease (CKD) and failure; other major factors include smoking, obesity, dehydration, poor diet (high sugar/salt/red meat), certain medications (NSAIDs), lack of sleep, and genetic conditions. These factors create a cycle where damaged kidneys worsen blood pressure, further damaging them.
10 Common Habits That May Harm Your Kidneys
The best drink for kidney repair and overall health is plain water, as it helps flush toxins, but mineral water, unsweetened green tea, black coffee (in moderation), low-potassium juices (like unsweetened cranberry), and herbal teas (like ginger or mint) are also great for variety and added benefits, while sugary sodas, alcohol, and coconut water should generally be avoided. Always consult a doctor for personalized advice, especially with kidney disease.
Early Signs of Kidney Disease
Vitamin C supplementation is contraindicated in blood disorders such as thalassemia, G6PD deficiency, sickle cell disease, and hemochromatosis. Avoid using supplements immediately before or after angioplasty. Patients with diabetes should supplement with vitamin C cautiously, as it can increase blood glucose levels.
Vitamin C. Many patients report that vitamin C causes bladder flares when they take supplements. Some studies found that vitamin C supplements can trigger the “need to go” in women. However, vitamin C naturally found in foods may not cause the same kind of bladder symptoms.
You should be able to get all the vitamin C you need by eating a varied and balanced diet. If you take vitamin C supplements, do not take too much as this could be harmful. Taking less than 1,000mg of vitamin C supplements a day is unlikely to cause any harm.
Taking more than 2000 mg daily is possibly unsafe and may cause kidney stones and severe diarrhea. In people who have had a kidney stone, taking amounts greater than 1000 mg daily increases the risk of getting more kidney stones. When applied to the skin: Vitamin C is likely safe for most people.
With a vitamin C content of 2,300 to 3,150 mg per 100g of pulp, Kakadu plum (Terminalia ferdinandiana; also known as gubinge or billygoat plum) is very likely the fruit with the highest content of vitamin C.
Vitamin C might react with the following:
Typically, the kidneys filter oxalate, and the body excretes it through urine. However, if a person with a kidney disorder consumes high levels of vitamin C, oxalate may start to build up inside their kidneys. This can lead to certain health issues, such as the formation of kidney stones.
You should start by eliminating, or at least cutting down, on the top seven irritants: coffee, tea, cola drinks, chocolate, alcohol, artificial sweeteners and cigarettes. You should allow at least two weeks without the food or drink before noticing any change in your bladder control.
Vitamin D. Recent studies found that women over the age of 20 with normal vitamin D ranges were much less likely to suffer from a pelvic floor disorder, like incontinence. If you suffer from a pelvic floor disorder it may be time to check your vitamin D levels through a simple blood test.
Vitamin C should not be mixed with acids, which includes all AHAs and BHAs. Vitamin C plays a key role in strengthening the outer layer of our skin barrier, but when combined with an acid, it can enhance the potency of your vitamin C and cause severe irritation [5].
Taking too much vitamin C can cause diarrhea, nausea, and stomach cramps. In people with a condition called hemochromatosis, which causes the body to store too much iron, high doses of vitamin C could worsen iron overload and damage body tissues.
Generally, earlier stages are known as 1 to 3. And as kidney disease progresses, you may notice the following symptoms. Nausea and vomiting, muscle cramps, loss of appetite, swelling via feet and ankles, dry, itchy skin, shortness of breath, trouble sleeping, urinating either too much or too little.
To improve kidney function, focus on lifestyle changes like staying hydrated, eating a balanced diet low in salt and processed foods, exercising regularly, quitting smoking, limiting alcohol, managing blood pressure and blood sugar, and avoiding kidney-harming medications like NSAIDs. Consulting your doctor for regular checkups and tailored advice, especially for protein intake, is crucial, as early intervention with healthy habits can slow disease progression.
You can check kidney function at home using at-home test kits for urine (detecting protein/albumin) or finger-prick blood tests (checking creatinine/eGFR), often with smartphone apps for analysis, or by monitoring symptoms like increased nighttime urination (nocturia), swelling, or changes in urine (blood, foam) and discussing results with a doctor, as home tests screen but don't replace professional diagnosis.