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Despite the fact that the human body can’t make vitamin C on its own, people usually get enough of this essential vitamin from different foods, making a deficiency uncommon (NIH, 2021). Still, some people take vitamin C supplements for the supposed health benefits. But, how much is too much vitamin C?
First things first: it’s not easy to overdose on vitamin C. It is a water-soluble vitamin, meaning it dissolves in water upon entering the body and the body doesn’t store it.
For example, when you consume more vitamin C than necessary the body doesn’t absorb all of it and excretes the excess amount in the urine. This is one reason why it’s difficult but not impossible to consume too much vitamin C (Lykstad, 2021; NIH, 2021).
For most adults, the recommended daily amount of vitamin C is around 100 mg a day, and the upper limit is 2,000 mg a day (NIH, 2021). Many foods that contain high levels of vitamin C still have less than 100 mg in one serving. This makes it difficult to get over 2,000 mg from food sources (NIH, 2021).
However, some supplements contain 1,000 mg in just one serving, making the possibility of overdose more likely if someone is taking several vitamin C supplements in a day.
What is vitamin C?
Vitamin C—or L-ascorbic acid—is a nutrient that is essential to human health, but the body can’t make it itself. Vitamin C is a water-soluble vitamin, meaning the body doesn’t store it in tissues like it does fat-soluble vitamins, such as vitamin D. This is why people need to consume regular and adequate amounts of vitamin C (NIH, 2021; Lykstad, 2021).
It is also an antioxidant, meaning it helps to neutralize “free radicals” that can be harmful to the body. By doing this, it may help delay or even prevent damage to your body’s cells (NIH, 2021; NIH, 2013).
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What does vitamin C do?
Vitamin C plays a critical role in several functions and helps the body maintain healthy structures. Without it, your body would not have healthy skin and connective tissue.
In addition to its role as an antioxidant, vitamin C helps your body fight infections, maintain a healthy immune response, absorb iron, and make collagen (Carr, 2017; Lystad, 2021; Abdulla, 2020). Collagen helps your body heal wounds, maintain strong and healthy skin, bones, ligaments, tendons, and functioning blood vessels (Wu, 2020; Abdullah, 2021).
Researchers are still trying to determine if vitamin C can help prevent diseases like cancer and cardiovascular disease. Currently, the evidence does not support this. However, it might help shorten the length of time that you have a common cold (NIH, 2021). Overall, there needs to be more research to determine the impact of vitamin C on health.
How much is too much vitamin C?
Most men over the age of 19 need about 90 mg of vitamin C a day. Most women over the age of 19 need about 75 mg a day. Women who are pregnant or breastfeeding require more, and people who smoke need about an additional 35 mg each day (NIH, 2021).
Most people get enough vitamin C from dietary sources, and supplements are usually unneeded. Many fruits and vegetables contain vitamin C, like tomatoes, oranges, peppers, grapefruit, strawberries, broccoli, and potatoes (NIH, 2021; Abdullah, 2021).
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A normal level of vitamin C in the body is between 300 mg and 2 g. If your level gets to 300 mg or below, you are deficient and may be close to developing scurvy. Symptoms of scurvy include poor wound healing, easy bleeding, muscle weakness, and muscle pain. (NIH, 2021; Abdullah, 2021). If your level gets too high, while uncommon, this may result in an overdose.
Can you overdose on vitamin C?
Most people get plenty of vitamin C from the foods they eat to meet the recommended dietary allowance. This is the amount that meets the nutritional requirements for most healthy people (NIH, 2021).
The general recommendation is that people over the age of 19 should not consume more than 2,000 mg of vitamin C in a day. This is called the “tolerable upper limit” intake —the maximum amount of a vitamin or mineral people can consume without the likelihood of experiencing adverse health effects (NIH, 2021).
The NIH notes that this tolerable upper limit intake recommendation does not apply to people who are receiving vitamin C as a form of medical treatment. But these people should also be under the care of a healthcare provider (NIH, 2021).
Getting vitamin C from food
People consuming vitamin C from dietary sources probably will not reach the 2,000 mg maximum intake recommendation. For example, red peppers are a high-content vitamin C food. But one-half cup of raw red peppers only contains 95 mg, meaning someone would need to consume over five cups of raw red peppers in one day before reaching the 2,000 mg limit (NIH, 2021).
Oranges also have a lot of vitamin C, but one medium orange only contains 70 mg. This means that someone would have to consume almost 29 oranges in one day before meeting the maximum recommended intake (NIH, 2021).
Getting vitamin C from supplements
If someone is taking a lot of vitamin C supplements, the possibility of consuming more than 2,000 mg in a day may be higher. It depends on the amount in the supplement and how many supplements someone is taking.
For example, if one serving of a supplement contains 1,000 mg, a person would only need to consume two of these in one day to already be at the 2,000 mg tolerable upper limit intake.
There may also be the possibility of adverse effects if someone gets IV vitamin C. IV vitamin C is sometimes used as a complementary treatment for pain relief. Experts have also explored using IV vitamin C in the treatment of patients who have COVID-19. More research is needed in this area (Abdullah, 2021; Carr, 2017; Huang, 2021).
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Symptoms of too much vitamin C
Overall, the effects of consuming too much vitamin C are usually not serious and include abdominal cramps, diarrhea, and nausea (NIH, 2021).
The body excretes vitamin C in the urine, so excessive amounts could contribute to the formation of kidney stones. This possibility is more of a concern in people with kidney disorders (NIH, 2021; Maxfield, 2020).
When it comes to your daily vitamin C intake, you can get adequate amounts through the food you eat. Usually, you do not need to consume vitamin C supplements to maintain healthy levels. While an overdose is unlikely, talk to your healthcare provider or dietitian before starting vitamin C supplements or if you have concerns about overdose based on your health history.
- Abdullah, M., Jamil, R. T., & Attia, F. N. (2021). Vitamin C (ascorbic acid). [Updated Jun 15, 2021]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK499877/
- Carr, A. C., & Maggini, S. (2017). Vitamin C and Immune Function. Nutrients, 9(11), 1211. doi: 10.3390/nu9111211. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5707683/
- Carr, A. C., & McCall, C. (2017). The role of vitamin C in the treatment of pain: new insights. Journal of translational medicine, 15(1), 77. doi: 10.1186/s12967-017-1179-7. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5391567/
- Huang, L., Wang, L., Tan, J., Liu, H., & Ni, Y. (2021). High-dose vitamin C intravenous infusion in the treatment of patients with COVID-19: A protocol for systematic review and meta-analysis. Medicine, 100(19), e25876. doi: 10.1097/MD.0000000000025876. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8133047/
- Lykstad, J., & Sharma, S. (2021). Biochemistry, water soluble vitamins. [Updated Mar 07, 2021]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK538510/
- Maxfield, L., & Crane, J. S. (2021). Vitamin C deficiency. [Updated Jul 18, 2021]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK493187/
- NIH. (2013). Antioxidants: In depth. Retrieved October 13, 2021, from https://www.nccih.nih.gov/health/antioxidants-in-depth
- NIH. (2021). Office of dietary supplements – vitamin C. Retrieved October 12, 2021 from https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/
- Wu, M., Cronin, K., & Crane, J. S. (2020). Biochemistry, Collagen synthesis. [Updated Sep 11, 2020]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK507709/
Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.