Patient Education Blog

Low Molecular Weight Heparins – Osteoporosis?

Occasionally, a patient is treated with long-term low molecular weight heparin (LMWH) (enoxaparin = Lovenox®; Dalteparin = Fragmin®; Tinzaparin = Innohep®) for months or years. LMWH may be given because the patient (a) tolerated warfarin poorly (widely fluctuating INRs; significant side-effects, such as marked hair loss or fatigue), (b) had a recurrent clot which occured on warfarin with a therapeutic INR, or (c) is pregnant and LMWH is the preferred “blood thinner” during pregnancy in women at increased risk for blood clots. The main side-effect of long-term LMWH is, of course, bleeding.

Whether LMWH causes osteoporosis (=loss of bone mass)  is not known, as it has not been appropriately studied. A recent detailed review of the literature concluded that (a) based on the evidence of reported cases and studies there may be a small impact of LMWH on osteoporosis, (b) no large studies have been done to investigate the effect of prolonged LMWH on bone density, (c) large well-designed clinical trials are needed to determine whether LMWH contributes to osteoporosis, and (d) it is impossible to say whether calcium supplementation is beneficial or not in patients treated long-term with LMWH.

My personal approach

In the absence of clinical trial data guiding physicians what’s right to do in the patient on long-term LMWH, I (a) recommend a once yearly bone density study (DEXA scan), and (b) encourage intake of daily calcium supplementation. No data whatsoever are available on long-term use of fondaparinux (Arixtra®) and osteoporosis. As with LMWH, I recommend a yearly bone density study and calcium supplementation.


Lefkou E et al. Low-molecular weight heparin-induced osteoporosis and osteoporotic fractures: A myth of an existing entity? Lupus 2010;19:3-12.

Disclosure:  I do not have a financial conflict of interest with the content of this post.

Last updated: June 22nd, 2011

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2 Responses to “Low Molecular Weight Heparins – Osteoporosis?”

  1. Dianne S. says:

    Most information I’ve read on low molecular weight heparin and osteoporosis notes “long term” enoxaparin usage as a risk, but I have not seen any warnings about short term usage for prophylaxis following surgery. Do you know if any studies on short term usage have been done or whether using lower prophylatic doses might decrease the risk of bone loss? Thank you very much.

    • Stephan Moll says:

      No study has looked at osteoporosis risk with short- term use (a few days or weeks) of prophylactic doses of LMWH after surgery. It is not likely that such a study would ever be done or considered to be necessary. Given that available data do not even show that longer-term prophylactic LMWH causes significant osteoporosis, there is not really a concern for osteoporosis with short-term prophylactic doses of LMWH. The small studies on prophylactic LMWH and osteoporosis that have been done have typically looked at use of LMWH for about 9-10 months (during pregnancy and the post-partum period).