Feeling "weird" and irritated after taking high doses of Vitamin C, like 0.5g (500mg), could be linked to a variety of side effects associated with large intakes of this vitamin. While Vitamin C is generally safe, excessive doses can lead to several side effects¹.

1. Nervous System Effects: Although not common, some individuals may experience mood changes such as irritability or feeling "weird." This can be due to the body's response to the excess amount being processed.

2. Gastrointestinal Issues: High doses (beyond the recommended daily amount of 65-90mg) can cause digestive disturbances, including nausea, diarrhea, and abdominal cramps due to the osmotic effect of unabsorbed Vitamin C in the gastrointestinal tract².

3. Potential Kidney Stone Formation: There is also a risk of kidney stones with high doses of Vitamin C, although this is more common at doses significantly higher than 500mg, or in individuals predisposed to kidney stone formation³.

The symptoms you're describing don't typically align with a Herxheimer reaction, which is more associated with a temporary increase in symptoms when certain infections are treated, often linked to antibiotic usage⁴.

If your symptoms persist or worsen, it might be worthwhile to discuss them with a healthcare provider to rule out any underlying conditions or sensitivities.

Footnotes

1. Mayo Clinic, "Is too much vitamin C harmful?" Mayo Clinic News Network, 2020. ↩

2. Office of Dietary Supplements, "Health Risks from Excessive Vitamin C", NIH, 2021. ↩

3. Mayo Clinic, "How much vitamin C is too much?", Mayo Clinic, 2022. ↩

4. MedlinePlus, "Ascorbic Acid (Vitamin C)", MedlinePlus. ↩