A dispute over pay means some vulnerable patients are having to come back for repeated blood tests, according to a health union.
About 37 workers who specialise in drawing blood, known as phlebotomists, from Gloucestershire Royal and Cheltenham General hospitals have walked out for a seventh week in a dispute over pay and grading.
Caroline Hayhurst, Cheltenham phlebotomist and Unison member, said healthcare assistants and nurses are not always able to take bloods from complex patients including children and profoundly disabled patients who have difficulties keeping their arms straight.
A hospital spokesperson said it had urged Unison to get round the table for talks.
"It is not accurate to suggest the trust has underpaid our phlebotomists when they are paid in line with the national profile," a spokesperson for Gloucestershire Hospitals NHS Foundation Trust added.
Hospital bosses added that they were not aware of large numbers of patients having to come back for repeated blood tests.
