After nearly 250 years of testing its troops’ strength, endurance and marksmanship, the U.S. military is starting to test their testosterone.

Defense Secretary Pete Hegseth says it will give them “the biological foundation required to sustain the fight,” brushing off concerns from current and former service members — including an ex-Army surgeon general — that the initiative rests on shaky science.

Some veterans fear the new mandatory screening could threaten troops’ fertility and careers, tying some of them to lifelong injections the Department of Veterans Affairs is not guaranteed to continue covering.

Under a program Hegseth announced in July, service members 30 and older will be screened each year for testosterone deficiency during their routine health assessments. Those found to have low levels will be offered hormone therapy.

Hegseth said treatment would be voluntary, though the Pentagon has not said whether troops who refuse recommended treatment would face consequences.

“We are building a High-T department focused on strength, performance, lethality,” the Pentagon’s chief spokesman, Sean Parnell, wrote on X in mid-September, echoing language used in podcasts and other forums with a recent focus on the definition of masculinity.

The rollout has been bumpy. The Pentagon posted clinical guidance for the screenings, for men and women, on Sept. 2; pulled it the next day, with an official calling it a draft that needed updates; and reissued it for men about two weeks later. The Pentagon has said guidance for women will come later but has not said when.

For the first time, the Pentagon has also put a number on what it wants. Troops who continue therapy while deployed must show, at a follow-up four to six weeks later, that their testosterone sits within a target range of 300 to 600 nanograms per deciliter, according to the Defense Health Agency’s guidance.

The program comes as the Trump administration pushes to widen access to testosterone therapy for men. After nearly a decade of decline, prescribing has been rising again since about 2022, and the American Urological Association has said up to a quarter of men who receive testosterone never had their levels tested before starting.

The Pentagon did not respond to MS NOW’s request for comment.

Hegseth unveiled the program on July 15 in a video titled “The High-T Department of War,” casting it as a way to keep the military on the “leading edge of lethality.” It is part of a broader campaign to toughen fitness and grooming standards across the force.

More than two months later, he was still selling it. In a Sept. 30 “State of the Force” address to junior officers and enlisted leaders at Marine Corps Base Quantico in Virginia, he boasted about the program: “The ideological clowns are out. The patriotic cowboys are in, with testosterone testing on top.”

It is highly unusual for a defense secretary to set medical policy himself, a job traditionally left to the services’ surgeons general and the Defense Health Agency. In April, Hegseth ended the military’s decades-old flu vaccine requirement, saying the department was “restoring freedom” to the force. By early June, an outbreak was spreading through basic training at Lackland Air Force base in San Antonio. By late June, every boot camp had reinstated the requirement

Dr. Ronald Blanck, a retired lieutenant general who was the Army’s surgeon general from 1996 to 2000, said the program “was clearly an attempt” by people “who really don’t know very much about medicine to increase aggressiveness and masculinity.”

Troops have long been able to get testosterone testing and treatment through Tricare, the military’s health insurance program.

What is new is routinely screening people who feel fine. Medical guidelines do not recommend testing men without signs of a deficiency, and the Endocrine Society has said the evidence does not support screening entire populations.

The Pentagon has not said how many people would be subject to mandatory screening. There were about 2 million members of the active-duty military and reserves as of 2024, the most recent figures available from the Department of Defense. About a third of them are over 30, and about 80% are male.

Blanck said the program stems from a flawed premise.

“‘If men have testosterone, then more testosterone would be better,’” he said, describing the thinking. “It’s not the way it works.”

Screening makes sense, Blanck said, when it finds a hidden problem that doctors can fix, like high cholesterol, which can be treated with statins. Testosterone, by contrast, declines naturally with age.

“I don’t have the level of testosterone at 80, almost 85, that I did when I was 25,” said Blanck, 84. “What if I took testosterone? Would I regain my 25-year-old body, virility and all that? No, it’s far more complicated.”

For men with a true deficiency, treatment can ease fatigue and build muscle. But for those whose levels are normal for their age, he said, it raises the risk of blood clots and will almost certainly cause infertility.

His advice to a 35-year-old service member who is passing fitness tests and might want children was blunt: “Don’t take testosterone. You will become infertile.”

Getting testosterone replacement therapy means monthly appointments, quarterly blood work and weekly injections, according to a service member with 23 years in the military who has been on the therapy for five years.

The service member was among those who spoke to MS NOW on the condition of anonymity because troops are not authorized to speak publicly about Pentagon policy.

The needles and vials go everywhere the military does, including to countries where testosterone is a controlled substance.

With last-minute travel, the service member said, the choice can come down to carrying a controlled drug across a border or leaving it behind and letting hormone levels crash for weeks. In the field, where troops can go weeks without a shower, it can mean injecting through dirty skin or skipping doses.

“In the field is where I need to perform the most,” the service member said.

One longer-term worry is cost. The therapy is usually lifelong, so a 30-year-old who starts while on active duty could rely on the VA for decades. “What is the guarantee that Congress is going to fund my mandatory injections?” the service member asked.

A second service member, with 19 years in the military, saw “real value” in treating genuine deficiencies but warned against the program becoming “a shortcut or a way to administratively separate those with low T scores.” Treatment, that service member said, should be “closely tied to medical guidelines.”

The Pentagon’s own guidance gives that concern some weight. It says a testosterone deficiency diagnosis does not by itself limit a service member’s duty or deployment, but troops in aviation, diving, submarine and nuclear jobs may be disqualified from those roles if diagnosed. Those fields already carry the military’s strictest medical standards, where new diagnoses and medications typically require special review.

Dr. Stephen Xenakis, a retired Army brigadier general who served 28 years on active duty and once commanded the Army hospital at Fort Campbell, Kentucky, said blanket screening breaks a basic rule of medicine. “You don’t treat the labs, you treat the patient,” he said.

He also questioned who would see the results. “Is it going to be held completely confidential? Is our commander going to have access to that data?” he said. “There was nothing I saw in any of the memoranda that worked through what would be the disclosure of that information.”

Picturing the order landing on his old hospital, he said every physician assistant, medical officer and flight surgeon would need training on what a low result means and who should be treated. “I don’t think we can implement it effectively,” he said.

Blanck said the testosterone program would cost the military more than it gained.

“They are wasting time and money on something that probably will have very little positive, quite possibly a lot of negative effect,” he said, “and instead they should be focusing on stuff that really will make a difference.”

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