For people who rely on certain prescription drugs, including weight loss, asthma and cancer medications, President Donald Trump’s post announcing 100% tariffs on foreign brand-name drugs offers little clarity on when — or if — medications might see price hikes.

“Starting October 1st, 2025, we will be imposing a 100% Tariff on any branded or patented Pharmaceutical Product, unless a Company IS BUILDING their Pharmaceutical Manufacturing Plant in America,” Trump said on Truth Social late Thursday. “‘IS BUILDING’ will be defined as, ‘breaking ground’ and/or ‘under construction.’ There will, therefore, be no Tariff on these Pharmaceutical Products if construction has started.”

Experts say Trump’s post raises a lot of questions. Here are five major ones.

What drugs will be impacted?

Trump’s post doesn’t specify whether brand-name drugmakers with an existing U.S. plant would be exempt, whether that exemption would include all their products, or whether it would only be for the drugs manufactured at the U.S. site.

Novo Nordisk and Eli Lilly, makers of the weight loss drugs Wegovy and Zepound, respectively, have announced plans to invest in U.S. manufacturing. But it’s unclear if their intent to invest will warrant an exemption.

On Tuesday, Lilly announced plans for a $6.5 billion manufacturing facility in Houston that will produce Zepbound and its other GLP-1 drug, Mounjaro, following a recent commitment to build a $5 billion plant near Richmond, Virginia. Novo Nordisk, a Danish company, said in June it would spend $4.1 billion to construct a second GLP-1 fill-finish plant in Clayton, North Carolina.

AstraZeneca, which makes the asthma drug Symbicort, also announced in July that it will invest $50 billion over the next five years to expand its research and development and manufacturing footprint in the U.S.

Many other popular brand-name drugs, however, are primarily manufactured overseas, particularly in Europe, said Rena Conti, an associate professor at Boston University’s Questrom School of Business.

Botox, made by Allergen, and the cancer drug Keytruda from drugmaker Merck are made in Ireland. (Keytruda’s manufacturing has increasingly moved to the United States in recent years, but it’s not clear if that would earn an exemption from Trump’s tariffs.)

Others, including some for blood and lung cancers, as well as vaccines, are made in places like India and China, Conti said.

“I think what’s most at risk here are branded products that come from China and India,” she said. The E.U. and Japan already have trade agreements in place that cover pharmaceuticals, she added, and it’s unclear whether the new tariff will supersede that.

Will patients see prices increase?

Only 1 in 10 of the prescriptions filled in the U.S. are for brand-name drugs; the vast majority are for generics, which are much cheaper and will not be affected by these tariffs.

Whether patients see price increases will depend on how many drugmakers receive exemptions — and on whether companies choose to pass those costs on to patients at the pharmacy counter, said Dr. Aaron Kesselheim, a professor of medicine at Harvard Medical School. ​​

“Ultimately, tariffs are taxes on patients,” Kesselheim said, “and to the extent that drug companies see increases in cost due to tariffs, they will pass those costs on to patients.”

Some companies may decide not to pass the costs along. So far, the 15% tariffs on imports from the E.U. haven’t translated into big price hikes for U.S. patients, Conti noted. To be sure, a 100% tariff would be far more costly for a company.

Price hikes may not start right away, as drugmakers find out whether they qualify for an exemption. There also might be a lag since U.S. law prevents drugmakers from increasing the price of drugs faster than inflation.

“What if you’re doing updates to the plant you currently have? What if you’re planning a facility? Do those count?” Kesselheim said. “It’s all very ambiguous.”

Some patients may not notice additional price hikes at all, given how costly brand-name drugs already are in the U.S., said Arthur Caplan, the head of the Division of Medical Ethics at NYU Langone Medical Center in New York City.

“I can certainly predict that some patients will immediately feel price increases that will shock them on some of these drugs,” Caplan said.

Could insurers absorb the costs?

Insurers and middlemen, known as pharmacy benefit managers, could try to negotiate drugmakers or absorb some of the tariff-related costs, Caplan said.

It’s more likely, however, that they’d pass it on to patients in the short term, potentially in the form of a larger copay, he said.

It’s not only patients with private insurance that should be worried about price hikes, Kesselheim said. Those who get their drugs covered through government health programs could also see price increases.

“The government is the largest purchaser of prescription drugs in the market, through Medicare, Medicaid and the VA, so it’s really the government or government payers that are going to see the largest impact on price increases,” he said.

Will tariffs spur more U.S. drug manufacturing?

It’s unlikely, Kesselheim said. The decision to build a plant “is a complicated and expensive one” that requires several regulatory hurdles and years of planning.

Conti noted that by the time new manufacturing plants are completed, Trump would likely be out of office.

“It is somewhere between two years and five years to get new production facilities built,” she said, “and it can be in the millions of dollars depending on whether the product that you’re making is a small molecule drug or a biologic.”

Even putting money back into an existing plant isn’t quick.

“If you want to switch a line or retool a factory to make a product, then we’re talking about somewhere between 18 to 36 months to do that,” Conti said, “because you have to show the U.S. regulator that you can make it at this factory at scale, and the product is what it says it is, or is high quality and meets the quality standards of the U.S.”

In a statement, Alex Schriver, a spokesperson for the trade group the Pharmaceutical Research and Manufacturers of America, said “most innovative medicines prescribed in America are already made in America” and companies continue to invest in the U.S.

“Tariffs risk those plans because every dollar spent on tariffs is a dollar that cannot be invested in American manufacturing or the development of future treatments and cures,” Schriver said. “Medicines have historically been exempt from tariffs because they raise costs and could lead to shortages.”

What about shortages?

If Trump keeps his focus solely on brand-name drugs, U.S. patients are unlikely to face shortages, Kesselheim said.

“Their profits are just so, so far beyond this tariff cost that they could probably be OK or raise the prices of the drugs,” he said. “They would probably not stop production as a result.”

But that excludes, he added, some smaller companies who may make niche brand-name products and may not have the resources to take on the extra costs. If tariffs extend to generics, the risk is far greater, Caplan added.

Unlike brand-name drugs, generic drugs are typically sold at close to the cost they’re made, he said, which makes it difficult for companies to justify the cost of building a new facility. They’d likely be forced to walk away from production or close their plants altogether.