Missed NHS appointments 'infuriating' for doctors
Nearly 300,000 people missed hospital outpatient appointments in Wales in 2016-17.
Health boards claim it cost more than £36m, although similar calculations have been questioned in the past because clinics are sometimes overbooked.
Dr Mike Fardy from the University Hospital of Wales said it was "infuriating" for medics and patients.
Some health boards use reminder texts to tackle the problem.