Witness Cherilyn Lee told jurors that Jackson complained he could not sleep and asked for the drug two months before he died.
She didn't know about propofol and talked to a doctor before warning Jackson it could kill him if he used it as a sleep aid.
"He told me that doctors have told him it was safe," Lee testified. "I said no doctor is going to do this in your house."
The singer, however, insisted the drug was the only thing that would help him sleep and that he would be safe as long as someone monitored him, she said. Jackson also said he had received propofol during surgery but didn't mention any doctors, she added.
Lee was the sixth witness called by defense attorneys for Dr. Conrad Murray, who has pleaded not guilty to involuntary manslaughter.
Authorities contend Murray gave Jackson a fatal dose of propofol. Attorneys for the Houston-based cardiologist have countered that Jackson gave himself the fatal dose after Murray left his bedroom.
Lee said she had treated Jackson for nutrition and energy issues as he prepared for his planned series of "This Is It" comeback concerts.
Jurors will hear more about the concert preparations through the testimony of Randy Phillips, the president and CEO of concert promoter AEG Live.
A judge on Tuesday blocked Murray's attorneys from asking Phillips about Jackson's contract with AEG for the comeback shows.
Defense attorneys had wanted to introduce Jackson's contract to show that he would be owe $40 million to the promoter if the concerts were canceled. The lawyers said Jackson would be desperate to make sure the shows continued and needed sleep to get through his rehearsals.
Superior Court Judge Michael Pastor said allowing testimony about the contract might confuse jurors.
"This is not a contractual dispute. This is a homicide case," Pastor said.
Murray's team also plans to call other witnesses who they think may support the theory that Jackson was desperate, including his makeup artist and hairstylist Karen Faye. They will also call several expert witnesses to rebut the testimony of prosecution experts who said Murray was reckless and at fault in Jackson's unexpected death.
Lee was the second medical professional who testified that Jackson inquired about propofol. Lee and Dr. Allan Metzger said they told Jackson it was unsafe to use as a sleep aid and shouldn't be given outside a hospital setting.
On cross-examination, Deputy District Attorney David Walgren recounted what Lee told police when she was interviewed.
"You told Michael Jackson, in response to his request for propofol, `No one who cared or had your best interest at heart is going to give you this,"' the prosecutor said.
Lee said that was true.
AP Special Correspondent Linda Deutsch contributed to this report.