Comorbidity
An additional condition present alongside the main one being treated.
What it means
A comorbidity is a condition existing alongside the one currently under consideration. Multimorbidity describes having two or more long-term conditions at once, which is the norm rather than the exception beyond about 65.
Comorbidities matter because they interact. Kidney disease changes which medicines are safe and at what dose. Asthma restricts beta blocker use. Depression alongside a physical condition worsens outcomes in both.
In practice
Clinical guidelines are written for single conditions studied in trials that frequently excluded people with comorbidities — which is why following several guidelines simultaneously can produce an unmanageable and sometimes contradictory regimen.
Why it matters
This is precisely where a structured review earns its place. The question is not whether each medicine is individually justified, but whether the whole set makes sense together for this person.
NICE has specific guidance on multimorbidity that explicitly permits departing from single-condition guidelines where the burden of treatment outweighs its likely benefit.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026