Does Too Much Vitamin C Cause Side Effects?

Vitamin C is water-soluble, which means it dissolves in water.

Unlike fat-soluble vitamins, water-soluble vitamins do not get stored in your body.

Instead, the vitamin C you consume gets transported to your tissues via body fluids, and any extra gets excreted in your urine (1).

Since your body does not store vitamin C or produce it on its own, it’s important to consume foods that are rich in vitamin C daily (1).

Even at high doses, vitamin C is not known to be toxic or to cause any serious adverse effects. The most common side effects are diarrhea, nausea, abdominal cramps, and other gastrointestinal issues (3).

Still, if you take larger-than-normal doses of this vitamin, your body can have difficulty processing it, and this can potentially lead to negative effects (4).

It’s important to note that vitamin C supplements are usually unnecessary because most people can easily get enough of this vitamin by eating fresh foods, especially fruits and vegetables (1).

Summary

Vitamin C is water-soluble, so it’s not stored within your body. If you consume more than your body needs, you’ll excrete the excess in your urine.

The most common side effect of high vitamin C intake is digestive distress.

In general, these side effects do not occur as a result of eating foods that contain vitamin C. They occur only as a result of taking high doses of vitamin C supplements.

You’re most likely to experience digestive symptoms if you consume more than 2,000 milligrams (mg) at once. Thus, a Tolerable Upper Intake Level (UL) of 2,000 mg per day has been established (1, 4, 5, 6, 7).

The most common digestive symptoms of excessive vitamin C intake are diarrhea and nausea.

Excessive intake has also been reported to lead to acid reflux, although scientific evidence does not support this (1, 5, 6, 7).

If you’re experiencing digestive problems as a result of taking too much vitamin C, you can simply cut back your supplement dose or avoid vitamin C supplements altogether (5, 6, 7).

Summary

Ingesting more than 2,000 mg of vitamin C per day may lead to gastrointestinal upset, including symptoms like diarrhea and nausea.

Vitamin C is known to enhance iron absorption.

It can bind to non-heme iron, which is found in plant foods. Your body does not absorb non-heme iron as efficiently as heme iron, the type of iron found in animal products (8).

When vitamin C binds with non-heme iron, it makes this iron much easier for your body to absorb. This is an important function, especially for individuals who get most of their iron from plant-based foods (9).

One study found that participants’ iron absorption increased by 67% when they took 100 mg of vitamin C with a meal (10).

However, individuals who have conditions that increase the risk of iron accumulation in the body, such as hemochromatosis, should be cautious with vitamin C supplements.

Under these circumstances, taking vitamin C in excess may lead to iron overload, which can cause serious damage to your heart, liver, pancreas, thyroid, and central nervous system (11, 12, 13).

That said, iron overload is highly unlikely if you don’t have a condition that increases iron absorption. Additionally, iron overload is more likely to occur if you consume excess iron in supplement form.

Summary

Since vitamin C increases iron absorption, consuming too much of it is a concern for individuals with conditions that lead to iron accumulation in the body.

Your body excretes excess vitamin C as oxalate, a waste product.

Oxalate typically exits your body via urine. However, under some circumstances, oxalate may bind to minerals and form crystals that can lead to the formation of kidney stones (14).

Consuming too much vitamin C has the potential to increase the amount of oxalate in your urine, thus increasing your risk of developing kidney stones (15).

In one study, when adults took a 1,000-mg vitamin C supplement twice daily for 6 days, the amount of oxalate they excreted increased by 20% (16).

High vitamin C intake is not only associated with greater amounts of urinary oxalate but also linked to the development of kidney stones, especially if you consume more than 2,000 mg per day (11, 17).

Instances of kidney failure have also been reported in people who have taken more than 2,000 mg in a day. However, this is extremely rare, especially in otherwise healthy people (18).

Summary

Consuming too much vitamin C may increase the amount of oxalate in your kidneys, which has the potential to lead to kidney stones.

Since vitamin C is water-soluble and your body excretes excess amounts within a few hours after you consume it, it’s quite difficult to consume too much.

In fact, it is nearly impossible to get too much vitamin C from your diet alone. In generally healthy people, any extra vitamin C consumed — beyond the Recommended Dietary Allowance — simply gets flushed out of the body (1).

To put it in perspective, you would need to consume 25 oranges or 14 red bell peppers before your intake reached the UL (19, 20).

However, the risks of vitamin C overdose are higher when people take supplements, and it is possible to consume too much of the vitamin in some circumstances.

For example, people who have conditions that increase the risk of iron overload or who are prone to kidney stones should be cautious with their vitamin C intake (11, 12, 17).

All the adverse effects of vitamin C, including digestive distress and kidney stones, appear to occur when people take it in doses greater than 2,000 mg (4).

If you choose to take a vitamin C supplement, it’s best to choose one that contains no more than 100% of your daily needs. That’s 90 mg per day for men and 75 mg per day for women (3).

Summary

It’s nearly impossible to consume too much vitamin C from food. However, if you’re supplementing with this vitamin, you can minimize your risk of getting too much by taking no more than 90 mg per day if you’re a man or 75 mg per day if you’re a woman.

Vitamin C is generally safe for most people.

This is especially true if you get it from foods rather than from supplements.

Individuals who take vitamin C in supplement form are at greater risk of consuming too much of it and experiencing side effects, the most common of which are digestive issues.

However, more serious consequences, such as iron overload and kidney stones, may also result from taking excessive amounts of vitamin C (5).

Fortunately, you can easily prevent these potential side effects by avoiding high dose vitamin C supplements.

Unless you have a vitamin C deficiency, which rarely occurs in generally healthy people, it is probably not necessary for you to take large doses of this vitamin.