Is Vitamin C Causing Side Effects? What You Should Know

Vitamin C is actually more likely to cause the opposite; loose stools or diarrhea, especially in high doses. Constipation is not a common side effect. In fact, some people use high doses of vitamin C as a gentle laxative.

However, if you’re taking a supplement that combines vitamin C with other ingredients, such as iron, the iron might be the real cause of constipation. Always check the full label to see what you're taking.

This is a common concern, especially with topical vitamin C products. For most people, vitamin C serums help brighten the skin and reduce inflammation. But in some cases, it may irritate, especially if:

• The concentration is too high for your skin type
• It’s combined with other harsh ingredients
• Your skin barrier is already damaged

A study notes that topical vitamin C can cause skin irritation, especially at concentrations above 20%. This irritation can show up as redness, small bumps, or what looks like a breakout. 

Technically, it’s not acne caused by clogged pores but a temporary reaction. Try switching to a lower concentration or using it less often to see if the issue improves.

Cold sores are caused by the herpes simplex virus, not by vitamin C itself. 

While there’s no strong evidence linking the two, one theory is that sudden changes in your immune activity could trigger a flare-up in people who already carry the virus.

If you're prone to cold sores, it’s worth keeping an eye on how your body reacts to supplements and adjusting your intake if needed.

Heart palpitations are not a known side effect of vitamin C in healthy individuals. But if you are taking very high doses (far above the recommended daily limit), it might affect other systems in your body, especially if you are also consuming other supplements or stimulants like caffeine.

In rare cases, people with underlying health conditions or sensitivities might notice changes in heart rhythm. 

Before taking high doses of vitamin C or combining it with other supplements, talk to your doctor, especially if you have a heart condition.

Yes, this is one side effect that does have some evidence behind it. High doses of vitamin C, especially over 2,000 mg per day, as per the National Institutes of Health (NIH), can increase the oxalate in your urine. Oxalate is one of the primary components of kidney stones.

If you have a history of kidney stones or are at risk, you should avoid megadoses of vitamin C. Speak to your doctor before starting supplements if you are concerned about kidney health.

Most people can take vitamin C without problems, even at night, especially in moderate doses. But in rare cases or with very high intake, some other side effects may appear:

• Headache: Some people report headaches with megadoses, especially over 2,000 mg.
• Fatigue or dizziness: Uncommon, but may occur with high or prolonged use.
• Bloating or gas: Vitamin C may mildly ferment in the gut, causing gas in some people.
• Tooth enamel erosion: Chewable vitamin C or powdered forms can wear down enamel over time if taken frequently without rinsing.

For most people, vitamin C is safe and well tolerated in reasonable amounts. But side effects can appear when:

• You are taking very high doses
• You mix it with other supplements or medications
• You have certain health conditions

Before taking vitamin C, especially in supplement form, it is a good idea to talk to your doctor. This is particularly important if you have pre-existing health conditions or are taking other medications.

If you notice anything unusual, whether it is breakouts, nausea, or something more serious, take a break and speak with a healthcare provider.