Elizabeth Holmes, the founder and CEO of lab-test startup Theranos, appeared on CNBC with Jim Cramer Thursday to defend her company against claims that its blood-test technology only works on a handful of tests.

A story in the Wall Street Journal said that Theranos uses machines bought from Siemens for the vast majority of its tests. Quoting unnamed sources and former employees, the story also said that Theranos had flubbed an important measure of quality control mandated by the Centers for Medicare and Medicaid Services.

"This is what happens when you work to change things," said Holmes. "First they think you're crazy, then they fight you, then all of a sudden you change the world."

Holmes took on the credibility of the Journal's sources, but was much less direct when asked how many tests could actually be run on her company's machines. She said that the people who spoke to the newspaper were people who had said as early as 2004 and 2005 "that there was no way I was going to succeed and build this kind of company." She said those people had questioned whether her name actually belonged on some early patents.

"It's pretty disappointing to see that every single one of the sources told us the statements [they were being asked to make] were false or misleading, and the only ones who were left wouldn't speak with us."

Holmes even claimed that one source said, in writing, that she could pay $2,500 if Theranos wanted to find out what the Journal had discussed with them. Holmes said the other sources work with Labcorp, one of her competitors.

The Journal story also said that Holmes refused to comment to them for five months. Holmes said she was given a three-day window. She said she also offered to bring her technology to the Journal offices and demonstrate it, but that the newspaper refused.

Holmes was less clear when asked, point-blank, how many tests her machine, dubbed Edison, could process. She said she'd submitted paperwork on 130 tests to the FDA, and that "every test we run can be run on our proprietary devices."