You have three years to make a claim for failure to treat negligence. All medical negligence claims are subject to limitation periods.
For example, in England and Wales, medical negligence claims must generally be brought, court proceedings issued within three years of the injury, or three years of knowledge of the facts giving rise to the claim.
If someone has passed away, the three years would start from the date of death if the limitation period has not already expired at the date of death.
Children not under a disability typically have until they reach 21 to start a failure to treat negligence claim or court proceedings.
Persons under a disability, who lack capacity, are not subject to any limitation period.