FDA warns about blood clot risk with testosterone products

Howard LeWine, M.D.

Chief Medical Editor, Harvard Health Publishing

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“Replacing” a hormone the body normally makes when it is running low isn’t necessarily the safest thing to do. Women and their doctors learned this with estrogen after menopause. Now the FDA is sounding a warning that testosterone therapy can cause potentially dangerous blood clots in men.

Blood clots that form in veins (what doctors call venous thromboembolism) come in two “flavors.” Deep-vein thrombosis, or DVT, is a blood clot that forms in a deep vein, often in the leg. It can make the affected leg swell or cause leg pain. If a DVT, or part of one, breaks away and gets into the bloodstream, it can block blood flow to the lungs. This is called a pulmonary embolism. A large pulmonary embolism can be deadly. Pulmonary embolism, along with DVT, kill as many as 180,000 Americans each year, more than the number of people who die from breast, prostate, colon, and skin cancers combined.

The FDA had previously warned about a testosterone-therapy-related increase in blood clots in men with a condition called polycythemia. Polycythemia is a condition in which the body makes too many red blood cells, which increases the risk of blood clots. Its latest warning comes from reports of blood clots in men without polycythemia.

The new warning is not related to the FDA’s evaluation of possible links between testosterone therapy and stroke, heart attack, and death.

Testosterone uncertainty

“Low T” is big business. You may have seen ads on television or in other media. Worldwide sales are expected to reach $5 billion by 2017. Testosterone is available as an injection, a gel, an underarm spray, and a nasal spray.

Advertisements for the male hormone imply it may be just what a man needs to boost his energy, mood, and sex drive. Then again, it may not.

Testosterone is made in the testicles. After age 30, most men’s testosterone levels begin to gradually fall. For some men, the decline is faster and steeper.

Experts are trying to come to grips with which men really need treatment with testosterone. Men whose bodies no longer make any testosterone, and those with extremely low levels of testosterone and classic symptoms of low testosterone definitely need treatment. Classic symptoms include:

  • low sex drive
  • low sperm count
  • loss of body hair
  • hot flashes

Few men fall into that category. Some men have symptoms that may or may not be related to low testosterone, like

  • difficulty concentrating
  • little interest in sex
  • feeling down
  • trouble sleeping
  • lower energy level
  • less “get up and go”
  • decreased muscle mass

Some men with at least one of these symptoms have low testosterone levels. But many others with one or more of these symptoms have normal levels.

Even if the testosterone level is low, it’s possible that these symptoms might be due to depression, low thyroid function, or some other medical problem. And there’s an evidence issue—we don’t really know who benefits from testosterone therapy.

Making the choice

Experts recommend testosterone therapy for men with a low testosterone level and one or more of the “classic” symptoms. For the rest? They get a talk-with-your-doctor recommendation.

The FDA’s warnings highlight that taking testosterone isn’t risk free. Combined with the lack of evidence about who really benefits, it means that the decision to start testosterone therapy is an individual one. A man must weigh the potential benefits against the potential increased risks of heart attack, stroke, and blood clots. If the balance tips in favor of moving forward, then trying testosterone is reasonable thing to do.


  1. Perry

    Hey Dan
    I am writing this from a hospital ICU. With blood clots in my lungs as I write this. I feel like an idiot for not properly researching testosterone which I bought from over the counter at GNC. Just wanted you to know you are not alone.

  2. Dan

    I’m currently Laying in a hospital bed in ICU as I write this. I’m in my mid 40’s & I was taking Testosterone shots every 2 weeks for the past few years. I have no known underlying conditions that are known. Over the past few days I had 2 CT scans & they have shown multiple blood clots in both lungs. I have been worried after I saw the study come out about the relationship between heart conditions, blood clots & low T therapy. Now I wish I would have taken those study’s far more seriously! Until now, I had no idea how painful blood clots in the lungs could be! I also don’t like the feeling of not being able to take a deep breath. I was one of those guys that thought the benefits outweighed the negatives. As it turns out, the neg. are far worse than I thought & I suggest to anyone thinking about low T therapy to think twice & really weigh your options. Please keep in mind, I was also an athletic guy in good physical condition with no underlying conditions before I started low T therapy & where I ended up certainly wasn’t better than the alternative!

    • Jim Strickland


      I am a TV reporter in Atlanta. Are you open to speking on camera about your situation?

    • mike

      Dan, hope you are doing better. I was on the testim cream, doctors painted me a nice picture, I did feel better, but now I am worse than ever. I had a mini stroke in 08 that left my left side of face numbed and a pulmonary embolism in 2012, in both lungs, I have not been the same since, shortness of breath, face numbed and have to be on blood thinners rest of my life, and I am only 53, was very athletic and not over weight.


  3. Kevin

    Many men are so concerned to increase their testosterone to improve their performance and hair growth, but testosterone can be very dangerous. Many doctors prescribe hormone therapy as a common remedy without thinking how it’s going to effect their patients

    • Kevin

      Make sure to consult a doctor before starting any hormone therapy, especially for hair regrowth. Dr.Umar at DermHair Clinic suggests that follicles that already have been damaged, can’t be repaired by any treatment, including testosterone treatment.

  4. Anonymus

    A coworker of mine passed away last week from what appears to be a blood clot in his leg. He had been taking Low T.

  5. al

    would be interesting to study if there is a relationship between exogenous administered T, the levels obtained and the risk of DVT. I’m not a fan of testosterone shots due to the fact that the peak level is much higher vs using a cream or gel.

    • Greg

      The answer to the peaks and valleys with shots is to due a series of blood tests to determine how quickly or slowly your body uses the testosterone. Mine uses it very fast and thus I’ve found that 1/2 cc twice a week is far better than 1 cc a week or a larger dose less often. I maintain a pretty steady 650 – 800 now as opposed to dropping to 200 or below if I wait 7 days between 1 cc shots. Also the shots are far far safer than gels, creams and sprays. I know several men besides myself on long term shots with no problems. All my doctors say the liver, kidney, heart and blood clot problems only started when these other forms came to be.

  6. Jeremy

    A little over a year ago I was not sleeping well at all and my wife complained about my excessive snoring and low libido. I’m 38 yrs old and take testosterone shots on a weekly basis prescribed by my doctor. I now do sleep better with very little snoring and my sex drive is way up, almost mid 20’s level again. However, I do worry about the long term affects of it. My doctor did state that I needed to go into it with some degree with uncertainty which is the case with most medicine treatments. There is a give in take with most things in life, it seems…

  7. Bio Chem Lab

    how to reduce Blood clots that form in veins ?

  8. John La Puma MD

    Most men are unaware of the usual cause of the Low T problem, and its effective fix.

    Losing weight in men means losing visceral fat first, which otherwise actively converts testosterone to estrogen. A 2012 Endocrine Society presentation reported an average drop of 17 pounds meant testosterone levels increased by 15 percent.

    Our own 2012 REFUEL study showed a 24 day average loss of 11 pounds with 75% reporting increase in muscular strength.

    Men like the idea of getting stronger, and generally dislike the idea of dieting. But men deserve to know more about their bodies, and to regain their health. The best medicine for “Low T” is often in the kitchen, instead of the clinic.

    John La Puma MD

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