Doctors can't figure out what is wrong with Michael.

Mr. Quintos, a Chicago resident, has constant stomach pain. He has been hospitalized, and his doctors have tried everything from antibiotics to antacids.

His doctors recommend that he have a computed tomographic (CT) Scan with contrast, which uses a special dye injected into the patient to better visualize their blood vessels and organs.

Hospitals have had to ration these tests because of a nationwide shortage of the agents needed for the procedure.

Mr. Quintos can't get an exam using the contrast dye.

He said that an alternative may not be enough to determine how to treat his illness.

50 million exams with contrast agents are performed each year in the United States, and as many as half the nation's hospitals are affected by the shortage. In emergency rooms, where quick, accurate assessments are the most dire, some people reserve a lot of their supply on hand.

The country's vulnerability to disruptions in the global supply chain and its overreliance on a small number of manufacturers for critical products is the latest example. GE healthcare is one of two major suppliers of iodinated contrast materials and operates the shuttered plant in Shanghai. The United States gets its dyes from the company.

In the wealthiest nation on Earth, there should be no reason for doctors to ration medical scans to make up for a shortage of material.

Robert Califf, the commissioner of the U.S. Food and Drug Administration, told a Senate committee that there was a shortage of contrast media.

The F.D.A. said it was working closely with manufacturers to help minimize the impact on patients, even though GE healthcare said this week that the situation was.

According to a statement from her office, Senator Patty Murray is pressing the agency to see what steps it is taking to address the shortage. She has introduced legislation to strengthen the supply chain.

The hits just keep on coming in the supply chain, said Dr. Jamie McCarthy, the chief physician executive at Memorial Hermann Health System.

When hospitals were overrun with Covid patients, they were facing large delays in getting tests, and elective procedures were canceled or postponed for months. Many patients have suffered worse health because they overlooked new symptoms or didn't get follow-up appointments. More cancer patients with advanced-stage disease are reported by some doctors.

The American Cancer Society is concerned about the impact of delayed, deferred or ignored screening.

The lack of contrast dye in an exam can make it more difficult to diagnose cancer, and it can make it harder to see if a treatment is working.

In addition to using contrast with aCT angiogram to determine if a patient has a blood clot or internal bleeding, doctors often useCT scans with contrast to spot infections, bowel obstructions or cancer. Some cardiac catheterizations are being delayed.

Some patients may be able to have an M.R.I. in place of aCT Scan or have the exam performed without contrast, because mammograms and lung cancer screenings do not require the agents.

Many patients are left in limbo because of the shortage.

Predicting how long the shortage will last is difficult. It feels like a never-ending marathon for health care workers because of the supply shortages.

ImageHealth care workers walked a residential street in lockdown in Shanghai on Monday. The city’s Covid precautions had affected a plant that manufactures contrast  dyes used in medical tests.
Health care workers walked a residential street in lockdown in Shanghai on Monday. The city’s Covid precautions had affected a plant that manufactures contrast dyes used in medical tests.Credit...Aly Song/Reuters
Health care workers walked a residential street in lockdown in Shanghai on Monday. The city’s Covid precautions had affected a plant that manufactures contrast  dyes used in medical tests.

The system uses contrast for procedures to preserve its supplies. He says that the volume of scans being done with contrast is half of what it normally is.

Kirk Garratt, the medical director for the group, said that the supply problem became a serious issue very quickly. He said that when other hospitals ran out of dye, they started sending patients to ChristianaCare.

Dr. Garratt said that they were really worried. He said that they needed to make the change now to make sure they have a supply of urgent care.

A patient who fails an exercise stress test that may indicate a heart problem but is not in imminent danger is likely to wait for a Scan and be treated with medication. If a patient enters the emergency room with chest pain and is sweating, an angiogram is needed to determine if they are suffering a heart attack.

If we don't fix that now, it will be too late to save you.

Hospitals rely on a single supplier for their contrast agents, and many facilities may have only a week or two of supply on hand, according to Dr. Matthew Davenport, vice chair of the commission on quality and safety for the American College of Radiology and a professor at Michigan Medicine.

The situation is similar to baby formula, where only a few companies serve a critical market.

GE healthcare said in a statement on Monday that it was increasing its supply of contrast media products, but did not give an estimate for when the shortage would end.

After having to close our manufacturing facility in Shanghai for several weeks due to local Covid policies, we have been able to reopen and use our other global plants wherever we can.

Within the next two weeks, the plant will be at 75 percent, according to GE healthcare. Increased production of the products at its plant in Ireland, as well as flying some shipments to the United States, are some of the steps it has taken.

The company said it was distributing the dye to hospitals based on their historical supply needs, which doctors said could prevent large hospital systems from storing excessive amounts.

According to Fulvio Renoldi Bracco, the other producer based in Milan, it was working to deliver supplies to hospitals that were not customers to shore up use for critical emergency procedures. He said that the F.D.A. had received a request from Bracco for the potential importation of an agent that had not been approved for use in the United States. The agency didn't comment on the request.

Nancy Foster, the vice president of quality and patient safety policy for the American Hospital Association, likened the situation to the short supply of oxygen, among other treatment machines and remedies, during the Pandemic. The group wants G.E. to give more information.

She said that we need to figure out how to create a much more robust, not as lean, supply system.