Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Stop using ascorbic acid and call your doctor at once if you have:
joint pain, weakness or tired feeling, weight loss, stomach pain;
chills, fever, increased urge to urinate, painful or difficult urination; or
severe pain in your side or lower back, blood in your urine.
Common side effects may include:
heartburn, upset stomach; or
nausea, diarrhea, stomach cramps.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Vitamin C side effects (more detail)
