Tiredness gets blamed on age. B12 is one of the few causes worth ruling out with an ordinary blood test — especially if you take metformin or long-term stomach acid tablets.
Persistent tiredness gets filed under age and never investigated. Seven common causes that each have an answer — and most of them are one blood test or one pharmacist appointment away.
The body gets worse at turning food into muscle with age — so the requirement rises. Why spreading it across three meals beats a bigger dinner, and why walking is half the answer.