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Can Tamoxifen cause false negative Pregnancy Test Result

Sarah38 Member Posts: 2


I'm hoping someone out there might be able to help me - I'm just wondering if it's possible that tamoxifen can cause false negatives for over the counter pregnancy test kits.

I'm 38 and have been on Tamoxifen for four and a half years. I was diagnosed 5 years ago with fairly advanced (metastasised) breast cancer and had to have 6 months of chemo followed by radical mastectomy and auxillary clearance, followed by concurrent milder chemo and 8 wks of radiation and finished treatment 11 months later. My periods stopped after the third month of chemo and have never come back. I did initially go into menopause from the chemo but about a year after I'd finished the chemo I had hormone tests which showed I was no longer menopausal and was ovulating and had a cycle. Until recently, I wasn't remotely worried about getting pregnant as I have not had a period in years. However in the past month I have been a little worried I might be pregnant (ridiculous I know - I feel stupid even writing it down when I've had no periods for 5 YEARS!), with symptoms of weight gain, tiredness, and very mild nausea, so I did a pregnancy test and it was negative. But I would like to know if the fact that tamoxifen is a hormone drug, means it could interfere with a pregnancy test? Does anyone know of any such cases. I started looking up websites this evening and now feel sick reading all the side affects to a baby if you take tamoxifen while pregnant. I know I'm being totally paranoid but if anyone has any information on this I would really appreciate it.

Thanks a mill!



  • mela4409
    mela4409 Member Posts: 3
    edited July 2010

    I'm wondering the same thing as you!  If you find anything out please post!  Freaking out right now!

  • latreen
    latreen Member Posts: 2
    edited July 2010

    I've been on tamoxifen for the past 17 months and it's not affected my periods so when I was 3weeks late I was concerned and did a pregnancy test a week ago and mine was positive. I rang my GP and she said I didn't have to go and have another test at the doctors to verify it so I'm thinking they must be pretty accurate although my husband did say it could give a false positive. 

  • Sarah38
    Sarah38 Member Posts: 2
    edited July 2010

    Thanks for that.

    I asked in a  few pharmacies and they couldn't give an answer as all literature is only about prevention rather than what to do if you think you are pregnant. So although I know it's ridiculous and I felt really stupid, I called the oncology day care centre where I was treated and they couldn't tell me either and said I'd need to get a blood test to be sure, so I did that and will get the result on Monday. I think it's a case that tamoxifen doesn't affect the home pregnancy tests but no one has the confidence to state this.

    I'm not too worried about it anymore as I don't think I'm pregnant and also I think if tamoxifen did interfere with pregnancy tests there would be warnings about it all over the place...I obviously just need to diet and do some exercise :-)

    They did say in the oncology day care that the chances of tamoxifen affecting a baby were miniscule and they had never come across any such cases, They went so far as to say they've given chemo to pregnant women in extreme cases and the babies have been perfect,  

    Thanks again,


  • latreen
    latreen Member Posts: 2
    edited September 2010

    Well here I am 16 weeks pegnant and growing! I went for the abortion as my onc suggested it was best and he had no stats for me, but the termination doctor had some for me and 98 out 104 babies conceived with tamoxifen were fine so we decided to go ahead with it. Anything wrong should show up in my 20 week scan (4weeks today) and so I am now preparing myself for that.

     I have heard of a lady being diagnosed whist pregnant and they gave her chemo too, which I thought was weird but its a different blood supply so its OK, as I remembered women with AIDS don't pass it on to their babies if they act quickly at birth.


  • Mrsmcg
    Mrsmcg Member Posts: 6
    edited February 2018

    I don't keep a good record of my periods, but I'm pretty sure my last one was after Christmas. Prior to this I have always had my periods regularly. I have taken Tamoxifen since last summer. I was diagnosed with idc in late January. I have been having stomach pains, which could be from anything. I did a home pregnancy test last week and it come back invalid. I mentioned to my cancer surgeon about the not having my period, and she asked how old I was (53 next week). She didn't even continue the conversation. Wondering if I should do another pregnancy test or if the chances of me being able pregnant are slim to none. I am concerned about taking Tami while pregnant!