The team at the University of Cambridge said this could be one of the easiest and safest sources of stem cells.
The cells were used to build blood vessels but experts cautioned that the safety of using such stem cells was still unclear, the BBC News reported.
Stem cells are one of the great hopes of medical research.
They can transform into any other type of cell the body is built from - so they should be able to repair everything from the brain to the heart, and eyes to bone.
One source of stem cells is embryos, but this is ethically controversial and they might be rejected by the immune system in the same way as an organ transplant.
Researchers have shown that skin cells taken from an adult can be tricked into becoming stem cells, which the body should recognise as part of itself and would not reject.
The team at Cambridge looked in blood samples for a type of repair cell that whizzes through the bloodstream repairing any damage to the walls of blood vessels. These were then converted into stem cells.
Dr Amer Rana said this method was better than taking samples from skin.
"We are excited to have developed a practical and efficient method to create stem cells from a cell type found in blood," she said.
"Tissue biopsies are undesirable - particularly for children and the elderly - whereas taking blood samples is routine for all patients," she added.
The cells also appeared to be safer to use than those made from skin, Rana told the BBC.
"The fact that these appeared to be fairly stable is very promising," she said.
"The next stage obviously is to say, 'OK if we can do all this, let's actually make some clinical grade cells', we can then move this technology into the clinic for the first time," she said.
"It's a hell of a lot easier to get a blood sample than a high quality skin sample, so that's a big benefit," said Professor Chris Mason, an expert on regenerative medicine at University College London.
"However, induced pluripotent stem cells (those converted from adult cells) are still very new, we need far more experience to totally reprogram a cell in a way we know to be safe," Mason added.
The study was published in the journal Stem Cells.