If you’re looking into treatment for certain types of breast cancer, your doctor might suggest Arimidex (anastrozole) as an option for you.

Arimidex is a prescription drug that’s used to treat certain types of breast cancer in adult females* who’ve gone through menopause. Specifically, Arimidex is prescribed in some cases for the following types of breast cancer:

This article describes dosage for Arimidex, including its form and strength. It also explains how to take the drug. To learn more about Arimidex, see this in-depth article.

Note: This article covers Arimidex’s typical dosages, which are provided by the drug’s manufacturer. But when using Arimidex, always take the dosage that your doctor prescribes.

* In this article, we use the terms “female” and “male” to refer to someone’s sex assigned at birth. For information about the differences between sex and gender, see this article.

Breast cancer term definitions

  • “Early” means that the cancer hasn’t spread beyond your breast or the lymph nodes in your armpit.
  • “Advanced” means that the cancer has spread into areas of your body near your breast or the lymph nodes in your armpit.
  • “Metastatic” means that the cancer has spread outside of areas near your breast or the lymph nodes in your armpit.

Below, you’ll find information about the dosage of Arimidex that’s typically prescribed.

What is Arimidex’s form?

Arimidex comes as a tablet that you swallow.

What strength does Arimidex come in?

Arimidex is available in one strength: 1 milligram (mg).

What are the typical dosages of Arimidex?

The information below describes dosages that are commonly used or recommended. But be sure to take the dosage your doctor prescribes for you. They’ll determine the best dosage to fit your needs.

Dosage for early breast cancer and for advanced or metastatic breast cancer

The typical Arimidex dosage is the same for early breast cancer and for advanced or metastatic breast cancer. This dosage is one tablet (1 mg) taken by mouth once daily.

Is Arimidex used long term?

In some cases, yes, Arimidex may be used as a long-term treatment. How long you’ll take Arimidex for depends on why you’re using it. If you and your doctor determine that Arimidex is safe and effective for you, you might use it long term.

Use for early breast cancer

Arimidex can be used after you’ve already had surgery to remove the breast cancer. When prescribed for this purpose, Arimidex is typically used until the cancer spreads or comes back.

Use for advanced or metastatic breast cancer

When used to treat advanced or metastatic breast cancer, you’ll take Arimidex for as long as your doctor recommends. In studies, when used for this purpose, Arimidex was typically taken for 5 years.

Here are answers to some common questions about Arimidex dosage.

Is there an FDA-approved Arimidex dosage used for bodybuilding?

No, there isn’t an Arimidex dosage for bodybuilding that’s approved by the Food and Drug Administration (FDA).

Arimidex is prescribed to treat certain types of breast cancer in adult females who’ve gone through menopause. The drug works by lowering estrogen levels in the body.

However, some bodybuilders use Arimidex to lessen side effects from anabolic steroids. Anabolic steroids are a human-made form of a hormone called testosterone. Bodybuilders may use these drugs in cycles (starting, stopping, and restarting their use). They’re used as a form of testosterone replacement therapy (TRT) to help muscles grow.

This type of steroid use can cause an increase in estrogen levels. In males, higher estrogen levels can cause gynecomastia (breast growth in males). When used with testosterone, Arimidex offsets the increase in estrogen levels. This helps prevent breast growth in males.

However, the FDA hasn’t approved Arimidex for use while bodybuilding, and it’s illegal to buy Arimidex for this purpose. You shouldn’t take Arimidex without a prescription from a healthcare provider. And you shouldn’t use the drug for conditions it hasn’t been prescribed to treat.

If you have questions about approved uses for Arimidex, talk with your doctor.

Will my dosage of Arimidex change if I take it with other drugs to treat my breast cancer?

It’s not likely. Depending on the type of breast cancer you have, you might use Arimidex with other drugs. But your Arimidex dosage will probably stay the same.

For advanced or metastatic breast cancer, Arimidex is typically used with targeted therapies. Targeted therapies work to attack cancer cells while causing little harm to healthy cells. Examples of targeted therapies include trastuzumab (Herceptin) and pertuzumab (Perjeta).

You may also use other drugs to help manage the side effects of Arimidex. For example, osteoporosis (weakened bones) is a common side effect of the drug. So, your doctor may prescribe drugs such as risedronate (Actonel) or alendronate (Fosamax) to help protect your bones.

For more information about using Arimidex with other drugs, read this in-depth article. And if you have questions about using Arimidex with other breast cancer treatments, talk with your doctor.

If you forget to take your daily dose of Arimidex, take your missed dose as soon as you remember. But if it’s almost time to take your next dose, skip your missed dose. Then, take your next dose at your usual time. You shouldn’t take any extra doses of Arimidex to make up for a missed dose.

If you’re not sure if you should take or skip your dose, ask your doctor or pharmacist.

If you need help remembering to take your dose of Arimidex on time, try using a medication reminder. This can include setting an alarm, downloading a reminder app, or setting a timer on your phone. A kitchen timer can also work.

The dosage of Arimidex you’re prescribed may depend on certain factors. The main factors that could affect your dosage are the type and severity of the breast cancer you’re using Arimidex to treat.

Your doctor will consider these factors when determining the most appropriate dosage for you.

Be sure to take Arimidex exactly as your doctor prescribes.

Arimidex comes as a tablet you’ll swallow. Your doctor will likely have you take your Arimidex dose once per day.

The drug can be taken at any time of day. But, if possible, it’s best to take your dose at the same time each day. This helps keep a consistent amount of the medication in your body at all times.

You can take Arimidex with or without food.

Don’t use more Arimidex than your doctor prescribes. Doing so can lead to serious side effects.

What to do in case you take too much Arimidex

Call your doctor right away if you think you’ve taken too much Arimidex. You can also call 800-222-1222 to reach the American Association of Poison Control Centers or use its online resource. But if you have severe symptoms, call 911 (or your local emergency number) immediately or go to the nearest emergency room.

The sections above describe the typical dosage provided by the drug manufacturer. If your doctor recommends Arimidex for you, they’ll prescribe the dosage that’s right for you.

Remember, you shouldn’t change your dosage of Arimidex without your doctor’s approval. Only take Arimidex exactly as prescribed.

If you have questions or concerns about your current dosage, talk with your doctor. Here are examples of questions you may want to ask your doctor:

  • Should my dosage change if I eat certain foods while taking Arimidex?
  • Does my dosage of Arimidex need to change if I’m taking certain other drugs along with it?
  • How long will Arimidex keep working for me after I’ve stopped taking the drug?

If you have breast cancer, you can subscribe to Healthline’s online newsletter. This resource provides helpful information and inspiring personal stories.


Instead of taking one Arimidex tablet once per day, can I take one-half of a tablet twice daily?

Anonymous patient


It isn’t recommended. You shouldn’t split, crush, or chew Arimidex tablets. Doing so may make Arimidex less effective in treating your breast cancer.

It’s important to take your dosage of Arimidex exactly as prescribed by your doctor. If you have trouble taking Arimidex once daily, talk with your doctor.

Melissa Badowski, PharmD, MPH, FCCPAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
Was this helpful?

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.