Patient Education Blog

Testosterone and Blood Clots

Testosterone Replacement Therapy

Replacement therapy with low doses of testosterone does not adversely affect blood coagulation status [ref 1] and does not appear to increase the risk of venous or arterial blood clots. Thrombosis is not listed as a potential side effect in a commly used drug compendium (Micromedex). Furthermore, the 2006 “Clinical Practice Guideline” from the Endocrine Society also does not list blood clots as a side effect of testosterone replacement therapy, or a previous history of blood clots as a reason not to give testosterone replacement therapy [ref 2]. However, the Androgel® package insert (prescribing information) lists “blood clots in the legs” as a potential side effect [ref 3], because one patient out of 163 patients on Androgel® developed a DVT over a 3 year period of time (details here). However, whether the DVT was caused by Androgel® or conicidental, is not known.

Anabolic Steroid Use/Abuse

Anabolic steroids are chemical variants of testosterone. They are taken in various doses, typically by athletes, to enhance muscle mass and physical performance. Several cardiovascular complications have been reported to occur in people using anabolic steroids, including high blood pressure, stroke, heart attacks (myocardial infarction), and pulmonary embolism [ref 4]. It is impossible to get a real sense of how frequent these complications occur, as it is difficult to find athletes for cardiovascular investigations who admit that they have taken anabolic steroids. Anabolic steroids taken long-term may increase the risk for arteriosclerosis (= hardening of the arteries), because they change the metabolism of blood lipids: the bad cholesterol LDL increases and the good cholesterol HDL decreases [ref 5]. Anabolic steroids may also lead to increased blood clot formation, even when taken only short-term, because they (a) increase levels of clotting factors (= pro-coagulant factors), (b) decrease levels of blood clot-dissolving proteins (= fibrinolytic proteins), and (c) make blood platelets more sticky (= lead to increased platelet aggregation) [ref 6].


Patient Questions /Examples – Explanations

Question #1: “I am 54 years old and had an unexplained leg DVT (deep vein thrombosis) 4 years ago. I was treated with warfarin for 6 months and have done fine since then. Because of a decrease in libido I was recently tested and found to have low testosterone levels in my blood. Is it safe for me to take testosterone or does it increase my risk for another blood clot?”

Answer #1:   Physiological testosterone replacement therapy does not appear to increase the risk for blood clots and appears to be safe to take.

Question #2: I have had one trauma-related DVT in the past (I’m no longer on warfarin) and have recently been diagnosed with low levels of testosterone – which was found following the discovery of a spinal compression fracture/ osteopenia. Does testosterone replacement therapy cause DVTs in men?

Answer #2: It does not. Furthermore, a history of DVT is not listed in the 2006 “Clinical Practice Guideline” of the Endocrine Society as a reason to not give testosterone therapy.



  1. Smith AM et al. Testosterone does not adversely affect fibrinogen or tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) levels in 46 men with chronic stable angina. Eur J Endocrinol 2005 Feb;152(2):285-91.
  2. Bhasin S et al. Testosterone therapy in adult men with androgen deficiency syndromes: an endocrine society clinical practice guideline. J Clin Endocrinol Metab.2006 Jun;91(6):1995-2010. Erratum in: J Clin Endocrinol Metab 2006 Jul;91(7):2688.
  3.  Last accessed March 15th, 2011.
  4. Vanberg, P et al. Androgenic anabolic steroid abuse and the cardiovascular system. Handb Exp Pharmacol. 2010;(195):411-57.
  5. Glazer G. Atherogenic effects of anabolic steroids on serum lipid levels. Arch Intern Med 1991;151:1925-33.
  6. Ferenchick GS. Anabolic-androgenic steroids and thrombosis: is there a connection? Med Hypothesis 1991; 35:27-31.


For Health Care Professionals: This same education blog, written for health care professionals, can be found here.

Disclosure: I have no financial disclosure relevant to this blog entry.

Last updated: March 18st, 2011

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2 Responses to “Testosterone and Blood Clots”

  1. Ron Sanftleben says:

    Hi Dr. Moll,
    Regarding Testosterone therapy and DVT – If testosterone therapy does not cause DVT do you know why lists the side affect
    “Blood clots in the legs. This can include pain, swelling, or redness of your legs”?
    My first DVT – massive, proximal, idiopathic in left leg – occurred while I was taking Androgel as prescribed. As no other cause was identified and Androgel lists blood clots as a side affect on their website, I had attributed my DVT to testosterone therapy – Perhaps incorrectly, as DVT #2 just happened though I no longer use testosterone.
    thanks much!

    • Stephan Moll says:

      The Androgel® package insert (prescribing information) lists “blood clots in the legs” as a potential side effect because one patient out of 163 patients on Androgel® followed in a 3 year observations study developed a DVT (I have added details and a relevant link in the text of the main blog above on this topic). This event was judged to be “possibly related to Androgel®)”. However, whether the DVT was caused by Androgel® or coincidental, is not known.