What Does Toxicity Mean on a Medicine Label?

What it means

Toxicity means the degree to which a substance can harm the body. With medicines, toxicity usually means a harmful effect that happens when the level in the body is too high, for example from an overdose, a drug interaction or reduced kidney or liver function. It can also mean harm to a particular organ, such as liver toxicity (hepatotoxicity), kidney toxicity, hearing damage (ototoxicity) or nerve damage (neurotoxicity).

Labels describe toxicity to tell you what to watch for and when monitoring is needed. Some medicines have a narrow gap between the helpful dose and a harmful one, so labels may ask for blood levels or regular tests. Leaflets list early signs of toxicity, such as new nausea, confusion, vision changes or unusual tiredness, depending on the medicine. Signs of an overdose need urgent help or a call to a poison control center.

Toxicity is different from an allergy, which is an immune reaction that can happen even at normal doses. It is also different from common, mild side effects.

Where you may see it

• Medicine labels under 'Warnings' and 'Overdosage'
• Therapeutic drug level reports (for example digoxin or lithium)
• Organ-specific warnings such as hepatotoxicity