Adverse effect of vitamins, initial encounter

This code identifies a patient's initial presentation with an undesirable or harmful reaction to a vitamin, when the vitamin was administered correctly and at a therapeutic dose. This adverse effect is an unintended consequence of the vitamin's pharmacological properties, not an overdose or poisoning.

Apply this code when a patient experiences symptoms such as nausea, rash, headache, or other adverse reactions following the appropriate intake of a vitamin supplement. This is used for the first encounter related to the adverse effect, before definitive treatment or resolution.

• Always assign an additional code for the specific manifestation of the adverse effect (e.g., R21 for rash, R11.0 for nausea).
• Distinguish carefully between an adverse effect (correct dosage) and poisoning (overdose), which uses different codes.
• Ensure documentation clearly states the vitamin involved and confirms it was an adverse reaction to a therapeutic dose.