- Tamoxifen is a SERM: it blocks estrogen in some tissues, such as the breast, and acts like estrogen in others.
- It’s used in PCT to raise LH and FSH, and to treat or prevent gynecomastia.
- It’s one of the most studied cancer drugs in history, prescribed for breast cancer since the 1970s.
- It’s a prescription drug in Canada; blood clots are its most important rare risk.
Nolvadex is the brand name that stuck for tamoxifen, a breast cancer drug that bodybuilders adopted for post cycle therapy and gynecomastia. This guide explains how it works, how it’s used medically, and what to know before using it.
How tamoxifen works
Tamoxifen is a selective estrogen receptor modulator. In breast tissue, it blocks estrogen, which is why it treats estrogen-sensitive breast cancer and gynecomastia. At the hypothalamus and pituitary, blocking estrogen’s negative feedback leads the brain to release more LH and FSH, which tells the testes to make testosterone and sperm. In bone and the liver, it acts more like estrogen.
Uses
Post cycle therapy
By raising LH and FSH, tamoxifen helps restart natural testosterone production after a steroid cycle. It’s often better tolerated than clomiphene. See our PCT guide.
Gynecomastia
Tamoxifen is used off-label to reduce painful or recent breast tissue growth in men, with the best results when started early. Long-established, fibrous gynecomastia usually doesn’t respond and may need surgery.
Male infertility
Some urologists use it off-label to raise sperm production in men with certain types of infertility.
Clinical reference doses
For breast cancer, the standard dose is 20 mg daily. Off-label use in men for gynecomastia or infertility commonly uses 10 to 20 mg daily under medical supervision.
Side effects
- Blood clots (deep vein thrombosis, pulmonary embolism): rare but serious; risk is higher with smoking, immobility or long flights
- Hot flashes and mood changes
- Eye changes with long-term use
- Liver enzyme changes
- Drug interactions: some antidepressants reduce its conversion to its active form
Seek urgent care for leg swelling or pain, sudden shortness of breath, or chest pain.
Legal status in Canada
Tamoxifen is a prescription drug in Canada (on Health Canada’s Prescription Drug List). It isn’t a controlled substance.
Buying Nolvadex in Canada
We stock Zionova Nolvadex and Nolvadex Genetix Pharma, both 20 mg tablets in bottles of 50; Genetix is cheaper at the time of writing. See our PCT page for live prices and a cost-per-day calculator. Comparing with clomiphene? Read our Clomid guide.
Frequently asked questions
What is Nolvadex used for in bodybuilding?
To help restart natural testosterone after a cycle and to treat or prevent gynecomastia.
Does tamoxifen lower estrogen?
No. It blocks estrogen at certain receptors but doesn’t lower estrogen levels; aromatase inhibitors do that.
Can tamoxifen reverse gynecomastia?
It often reduces recent, tender breast tissue. Older, fibrous gynecomastia usually needs surgery.
Is Nolvadex legal in Canada?
It’s a prescription drug and not a controlled substance.
Products mentioned in this guide
This article is general information for adults in Canada, not medical advice. Talk to a doctor or pharmacist before using any prescription drug, anabolic steroid or research compound, and get bloodwork done. If you’re in crisis, call or text 9-8-8 (Suicide Crisis Helpline) any time.
