(CNN) -- Many West Coast residents came up empty handed in their search of potassium iodide this week as fears over radiation spreading from Japan took hold.
The rush on the supplement came even as emergency management officials said there is no need to take the pills believed to prevent the thyroid from absorbing radiation.
"I didn't see too many people concerned about it. But when it was sold out, it made me think that I should be concerned," said Hameed Hemmat, who lives in the San Francisco Bay area.
Hemmat, who struggled to find potassium iodide online when he couldn't find it in his area, said he ended up placing an order with a New Jersey company. He also has friends in New York looking for it.
Last week's 9.0-magnitude earthquake unleashed a deadly tsunami that wiped out large sections of northeastern Japan. The waves damaged a nuclear power plant that has released radiation into the air and could release more if workers can't control runaway temperatures.
The U.S. Nuclear Regulatory Commission has said it does not expect to see harmful levels of radiation reaching the United States from Japan, but is working to deploy additional monitoring capabilities to parts of the western United States and U.S. territories.
Some, like Angie Girgis in Dublin, California, said the crisis in Japan is not a cause for alarm stateside.
"It's pretty far away," Girgis said. "There's a whole ocean between us."
Others, like Matt Donnellan in San Diego, said it was a case of being prepared.
"I sent some to my family in New York and kept some just in case," he said.
Internet retailers attempted to capitalize on the fear. A Twitter search revealed dozens of of ads hawking the product.
The supplement disappeared from some store shelves even as California's emergency management agency warned residents against taking it.
"It is not necessary given the current circumstances in Japan," the agency said. "It can present a danger to people with allergies to iodine, shellfish or who have thyroid problems, and taken inappropriately it can have serious side effects."
Diane D'Arrigo with the Nuclear Information and Resource Service in Washington, D.C. said she's ordered potassium iodide, but acknowledges it has limited effectiveness.
"It is important for blocking uptake of (radioactive) iodine to the thyroid, but there are other radionuclides that go to other organs that it won't help with," she said of the radioactive elements.
The Nuclear Information and Resource Service bills itself as a center for "citizens and environmental activists concerned about nuclear power, radioactive waste, radiation and sustainable energy issues."
Some who came away unsuccessful in their search for potassium iodide took other steps.
Jamie Everhart of Hungtington Beach, California, opted for sea kelp instead.
"Sea Kelp is a natural source of iodine which blocks the radiation from processing in your thyroid," she said. "I figure it's better to be safe than sorry."
CNN's Lateef Mungin and Nick Valencia contributed to this report.