Tamoxifen Dosages for Adults: Your GoodRx Guide

Tamoxifen (Soltamox) is an oral medication that’s primarily used to treat breast cancer. Tamoxifen is a type of medication called a selective estrogen modulator (SERM). This means it works by blocking or activating estrogen effects in different parts of the body.

Tamoxifen is effective for treating and preventing estrogen receptor-positive breast cancer because it blocks estrogen’s effects in the breasts. But it’s also been studied for treating many other types of cancer and other conditions.

If you or a loved one has been prescribed tamoxifen, it helps to know what to expect. Your prescriber will likely cover possible side effects and drug interactions. They’ll also recommend a specific dose, so be sure to follow their instructions. Here, we’ll cover common tamoxifen dosages to be aware of.

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What’s the typical tamoxifen dosage?

Tamoxifen is FDA approved for treating and preventing breast cancer in adults. It’s available as oral tablets and also as an oral solution called Soltamox. Your tamoxifen dosage will depend on how advanced your breast cancer is.

Most people take tamoxifen for at least 5 to 10 years to help prevent cancer from regrowing or coming back. Tamoxifen is usually taken once a day, and you can take it with or without food.

Tamoxifen dosage for ductal carcinoma in situ

Ductal carcinoma in situ (DCIS) is early-stage breast cancer that’s contained within the milk ducts. It’s a non-invasive stage of cancer. But it can become invasive, spreading to new tissue over time, especially if it’s not treated.

The typical tamoxifen dosage for DCIS is 20 mg by mouth once a day for 5 years.

Tamoxifen dosage for adjuvant treatment of breast cancer

Adjuvant treatment means that tamoxifen is taken after having surgery for breast cancer. Taking tamoxifen after having surgery reduces the risk of the cancer coming back. It can also help the surgery be more successful.

The recommended tamoxifen dosage for adjuvant treatment is 20 mg by mouth once a day for 5 to 10 years.

EXPERT PICKS: WHAT TO READ NEXT

• Is tamoxifen chemotherapy? Read pharmacists’ answers to this and other frequently asked questions about tamoxifen.

• What side effects can happen? Learn more about tamoxifen’s side effects — from hot flashes to swelling — and how to manage them.

• How does tamoxifen work? Find out from our GoodRx-perts how tamoxifen treats and prevents breast cancer.

Tamoxifen dosage for metastatic breast cancer

Metastatic breast cancer is the most advanced stage of breast cancer. In this stage, the cancer cells have spread to other parts of the body such as the bones, lungs, or brain. And it tends to be the most difficult type of cancer to treat.

The usual tamoxifen dosage for metastatic breast cancer is 20 to 40 mg per day. If you’re taking a 40 mg dose, your prescriber will likely recommend taking 20 mg twice a day (morning and evening).

Tamoxifen dosage to lower the risk of breast cancer

Tamoxifen can help lower the risk of developing breast cancer for those who have a high risk for it. The typical tamoxifen dosage to reduce the risk of breast cancer is 20 mg once a day for 5 years.

Are there any dosage adjustments for health conditions?

Some medications may need different dosages for people who have kidney or liver problems. But that’s not the case for tamoxifen. There are no recommended dosage adjustments for people with certain health conditions.

But tamoxifen can cause liver problems in some people, including elevated liver enzymes and, very rarely, liver cancer. If you have a history of liver problems, be sure to let your prescriber know. They’ll likely monitor your liver function with regular blood tests while you’re taking tamoxifen.

What happens if you miss a dose of tamoxifen?

If you miss a dose of tamoxifen, take the missed dose when you remember. But if it’s almost time for your next scheduled dose, skip the missed dose. Then, take the next dose at your regular time. Don’t take an extra or double dose to make up for a missed dose.

If you find that you’re missing doses frequently, let your prescriber know. It may affect how well your breast cancer is treated. There are also tools and tips to help you remember your doses. Examples include setting alarms on your phone, downloading a medication reminder app to a smartphone, or using a pill organizer.

What should you do if you take too much tamoxifen?

If you accidentally take an extra dose of tamoxifen, it’s not likely to cause serious harm. But you may experience worse side effects, such as nausea, swelling, or hot flashes. Let your healthcare team know if you experience severe or persistent side effects.

Taking a large amount of tamoxifen can have more dangerous effects. Tremors, abnormal heart rhythms, and seizures are possible. Call Poison Control at 1-800-222-1222 or your prescriber right away if you or someone else takes a large amount of tamoxifen. If you notice symptoms that seem severe or life threatening, such as loss of consciousness or confusion, seek immediate medical help at the nearest ER or by calling 911.

How to save on tamoxifen

GoodRx can help you navigate options to save on tamoxifen, which is available as a generic medication and as brand-name Soltamox. With a free GoodRx discount, you can save over 75% off the average retail price of generic tamoxifen at certain pharmacies. The price of a one-month supply of generic tamoxifen could be as low as $42.04 with this discount.

There are also ways to save on brand-name Soltamox:

• Save with a manufacturer copay card. If you have commercial insurance, you could pay as little as $0 per month with a copay card.

• Save with a patient assistance program. If you’re uninsured or underinsured, you may be eligible to receive Soltamox free of charge.

Why trust our experts?

Written by:

Austin Ulrich, PharmD, BCACP

Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. In his early career, he provided direct patient care in a variety of settings, including hospital and community pharmacies, and in a primary care clinic as a clinical pharmacist.

Edited by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Reviewed by:

Sonja Jacobsen, PharmD, BCPS, BCOP

Sonja Jacobsen, PharmD, BCPS, BCOP,  is a clinical oncology pharmacy specialist currently practicing in Seattle. She has been practicing as a pharmacist since 2015 and is licensed to practice in Washington state and North Carolina.

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