Avoiding Vitamin C Overload: Benefits and Risks

Vitamin C is a water-soluble vitamin, which means the body can flush out excess vitamin C that it doesn’t need. While this reduces the risk for vitamin C overdose/toxicity, it’s still possible to experience symptoms if you take too much vitamin C in supplement form.

What are the side effects of too much vitamin C? Some can include diarrhea, heartburn or other digestive issues, headaches, high iron levels, and potentially kidney stones.

How can you get the many vitamin C benefits (sometimes called ascorbic acid) without ingesting too much? The very best way is to get this vitamin naturally by eating vitamin-C rich foods — some of the best being citrus fruits, green vegetables, berries and squash.

What Does Vitamin C Do?

Vitamin C has many roles when it comes to promoting health, such as:

• Acting as an antioxidant, helping protect against free radical damage and slowing the effects of aging.
• Counteracting the negative effects of sun damage, cigarette smoke, air pollution and other environmental stressors.
• Supporting the immune system to protect against illnesses.
• Helping form collagen and maintain connective tissue, including the skin, bones, joints and blood vessels.
• Supporting eye health/vision and potentially reducing the risk for cataracts.
• Helping reduce the risk of certain types of cancers and cardiovascular disease.
• Facilitating absorption of iron.

Certain people can benefit from getting even higher amounts of vitamin C than the general population, including those who:

• smoke or around secondhand smoke
• people who eat a poor diet lacking vegetables and fruits
• those with medical conditions, such as severe malabsorption, cancer and kidney disease

Researchers shows that vitamin C deficiency symptoms most often affects those with severe malnourishment, drug and alcohol abusers, or those living in poverty.

How Much Is Too Much Vitamin C?

While vitamin C is generally considered safe and a widely consumed supplement for its immune-boosting effects, taking high doses of vitamin C can cause a number of side effects. Generally speaking, experts recommend taking no more than 2,000 milligrams per day of vitamin C, especially if taking high doses for weeks or months on end.

The recommended daily allowance (RDA) of vitamin C for adults is between 65 to 90 milligrams (mg) per day depending on someone’s age, while the safe upper limit is 2,000 milligrams a day, according according to the National Institutes of Health (NIH).

Certain studies have found that taking between 200 and 500 milligrams per day is plenty to experience health benefits and that doses higher than this may not even be absorbed. If you take too much vitamin C, you urinate the extra amount out, which can mean that high-dose supplements serve no purpose.

How much vitamin C can the body absorb in 24 hours?

There’s some evidence that 200 milligrams per day is the maximum amount of vitamin C that human cells can absorb. However, according to the Linus Pauling Institute, “There is no reliable scientific evidence that doses of vitamin C up to 10 g/day (10,000 milligrams) in adults are toxic or detrimental to health.”

What is a normal vitamin C level?

Vitamin C levels in the blood of less than 0.3 mg/dL are considered an indication of significant vitamin C deficiency, while levels above 0.6 mg/dL indicate sufficient intake.

How much vitamin C do children need? For example, is 500 mg of vitamin C too much for a child?

Below is the average daily recommended amounts of vitamin C for children of different ages:

• Birth to 6 months: 40 mg/day
• Infants 7–12 months 50 mg/day
• Children 1–8 years: 15 to 25 mg/day
• Children 9–13 years 45 mg/day
• Teens 14–18 years: 65 to 75 mg/day

According to the NIH, children between the ages of 1–3 years should not take more than 400 mg/day of vitamin C, children 4–8 years should not take more than 650 mg/day and children between 9–13 years should not exceed 1,200 mg/day. These are considered the safe upper limits, so supplementing with more may potentially cause side effects.

Can you overdose on Emergen-C?

Emergen-C products, which typically contain a high vitamin C dosage of about 1,000 milligrams, are unlikely to cause any serious overdose symptoms. If you feel sick or have a health condition that means you could benefit from extra vitamin C, then taking 1,000 milligrams may be beneficial, but doses over this amount may not be absorbed or provide any benefit.

Signs and Symptoms of Too Much

Taking very large doses of vitamin C has been shown to cause an overdose in this vitamin, also referred to as vitamin C toxicity. Some symptoms of vitamin C overdose can include:

• Digestive issues like diarrhea, nausea or abdominal cramps
• Heartburn
• Headaches
• Insomnia
• Accumulation of iron, which can damage tissue

Vitamin C Overdose Dangers and Complications

In rare instances, such as in some cases reports, serious adverse reactions/side effects of vitamin C overdose have been found to include:

• Kidney stones
• Increased oxidative stress
• Excess iron absorption
• Vitamin B12 deficiency
• Erosion of dental enamel
• Birth defects
• Cancer
• Atherosclerosis
• Rebound scurvy

Levels of vitamin C in the blood are controlled by the kidneys. One of the biggest concerns with vitamin C overdose is the risk for kidney stone formation, so vitamin C supplements are not usually recommended for men and others at risk for oxalate stones.

Very high doses can acidify the urine, cause digestive issues and interfere with antioxidant balance in the body. Among people who have the conditions thalassemia or hemochromatosis, too much vitamin C can cause iron overload.

What effects can taking too much vitamin C during pregnancy have?

Pregnant women need about 85 milligrams per day of vitamin C, while breastfeeding women require about 120 mg/day. Too much vitamin C during pregnancy can lead to diarrhea, nausea and possibly dehydration, which can pose a risk to the baby.

It’s possible these effects can impact levels of amniotic fluid, especially if vomiting and severe dehydration occur over long periods of time.

How to Treat and Prevent Vitamin C Overdose

The single best way to prevent vitamin C overdose is to avoid taking supplements in high doses and to get the vitamin C your body needs from foods instead, especially fresh vegetables and fruits. Some of the foods richest in vitamin C include citrus fruits like oranges, leafy green vegetables, red peppers, melon, berries, kiwi, mango and sweet potatoes.

As mentioned above, vitamin C is water-soluble. What does this mean in terms of getting extra vitamin C out of your body? Do you pee out excess vitamin C?

Because vitamin C is water-soluble, it’s not as risky to take too much vitamin C as it is to take fat-soluble vitamins like vitamin A or D. Unmetabolized ascorbic acid (vitamin C that is isn’t needed) is excreted in the urine.

That said, overdose of vitamin C is still possible if someone takes supplements in high doses for an extended period of time, especially if that person also consumes lots of vitamin C from his or her diet and/or fortified foods.

How long does it take to get vitamin C out of your system?

Vitamin C can stay in the body for weeks. However, excess amounts are usually urinated out in a matter of hours.

Vitamin C will stay in someone’s body longer if that person doesn’t already have high levels or are deficient. In order to prevent vitamin C from being lost in the urine, it’s best to take smaller, multiple doses spread out throughout the day.

Risks and Side Effects

People taking certain medications or who have certain health conditions should not supplement with vitamin C (especially in high doses) because vitamin C can interact with a number of drugs.

Vitamin C may interfere with medications including:

• certain cancer treatments (potentially chemotherapy)
• birth control pills
• aspirin
• drugs used to control cholesterol levels
• blood-thinning drugs, such as warfarin (Coumadin)
• antipsychotic drugs (like luphenazine or Prolixin)
• the antiretroviral drug Crixivan

Anyone taking these medications should avoid taking high doses of a vitamin C supplement without supervision from a doctor.