If you’re feeling dizzy, you may wonder if your medication could be causing it. “I just can’t seem to pinpoint the cause of my dizziness,” one member of MyBCTeam said.

Dizziness is a possible side effect of tamoxifen (Soltamox), which may be used to treat breast cancer or reduce your risk of developing it. Keep reading to learn about the possible causes of dizziness and how tamoxifen could be involved.

What Causes Dizziness?

Just as there are many ways to describe dizziness, there are many possible causes. For example, you might feel dizzy if something affects your sense of balance.

Your brain uses information from your eyes, ears, muscles, skin, and nerves to tell your body how to stay balanced. If any part of this system isn’t working well, you may feel dizzy.

Several health conditions — including ear, heart, neurologic, and other conditions — and medications can also cause dizziness.

Inner Ear Conditions

The vestibular system in your inner ear plays an important role in balance. Inner ear disorders, such as benign paroxysmal positional vertigo, and ear infections can disrupt your sense of balance and make you feel dizzy.

It’s possible to have more than one cause of dizziness while taking tamoxifen. A MyBCTeam member starting tamoxifen commented, “I’m a little nervous because I already have dizziness issues from a bad ear.”

Heart Conditions

Heart and blood vessel problems can affect blood flow to your brain and make you feel dizzy. Examples of heart-related problems that can cause dizziness include:

• Hypotension (low blood pressure)
• Arrhythmia (irregular heartbeat)
• Atherosclerosis (narrowing of the arteries)

Some breast cancer treatments can cause cardiotoxicity (damage to the heart). One possible heart problem is heart failure, in which the heart can’t pump blood as well as it should.

Breast cancer treatments that can cause heart problems include:

• Doxorubicin
• Trastuzumab (Herceptin and its biosimilars)
• Radiation therapy
• HER2-targeted therapy treatments, including fam-trastuzumab deruxtecan-nxki (Enhertu) and pertuzumab-containing regimens

The risk of heart problems varies depending on the treatment and the individual.

Neurologic Conditions

Conditions that affect the brain or nervous system can also cause dizziness. For example, dizziness can be a migraine symptom. According to Cleveland Clinic, migraine headaches affect about 12 percent of Americans and are especially common among women.

“I have a history of migraine. After taking tamoxifen, I developed daily dizzy spells and was diagnosed with migraine-associated vertigo (MAV). Basically, my migraine changed into a monster,” one MyBCTeam member shared.

The condition formerly called MAV is now commonly known as vestibular migraine.

Other Medical Conditions

Additional conditions that often cause dizziness include:

• Anemia
• Dehydration
• Anxiety
• Heat exhaustion
• Postural tachycardia syndrome

Medications

Dizziness is a possible side effect of many medications, including:

• Antihistamines (allergy drugs)
• Antidepressants
• Pain medications
• Blood pressure medications

Breast cancer treatments that may cause dizziness include:

• Some types of chemotherapy
• Trastuzumab
• Hormonal therapy, including tamoxifen, as well as anastrozole (Arimidex), exemestane (Aromasin), fulvestrant (Faslodex), letrozole (Femara), and toremifene

Some newer targeted therapies used with hormonal therapy for advanced breast cancer can also contribute to dizziness.

Several MyBCTeam members have wondered whether others experience dizziness while taking breast cancer treatments. For instance, they have asked:

• “Does anyone have heart palpitations and dizziness while taking paclitaxel?”
• “Anyone else have dizziness while taking letrozole?”

Is Dizziness a Side Effect of Tamoxifen?

Dizziness is listed as an infrequent side effect of tamoxifen. It isn’t clear exactly why some people experience dizziness while taking tamoxifen. Dizziness may occur on its own or along with other side effects that could contribute to feeling dizzy.

Menopauselike side effects, including hot flashes (hot flushes), vaginal dryness, and night sweats, are common with tamoxifen. Hot flashes can make you feel overheated and sometimes occur along with dizziness.

Tamoxifen can also increase the risk of developing cataracts (cloudy areas in the lens of the eye that can cause blurred vision). Vision changes can sometimes contribute to feeling dizzy.

How Is Dizziness Managed?

“There is nothing fun about dizziness or falling!” commented a MyBCTeam member. If you experience dizziness, you can take the following steps to help prevent falls and injuries:

• Sit or lie down as soon as you start to feel dizzy.
• Stand up and sit down slowly.
• Try not to move your head too quickly.
• Keep your living area well lit and free of clutter that could cause you to trip.
• Wear supportive shoes.
• Use a cane or walker if needed.
• Keep your phone with you so you can call for help if you fall.
• Avoid driving or using machinery while you feel dizzy.

Limiting certain substances may help if they make your dizziness worse. These include:

• Caffeine
• Alcohol
• Tobacco

Your doctor may recommend restricting salt if you also have a condition that causes dizziness, such as Ménière’s disease.

When Should You Call a Doctor?

For some people, dizziness improves as their body adjusts to treatment. Tell your oncologist or another member of your healthcare team if dizziness doesn’t go away, keeps coming back, gets worse, or bothers you. Your doctor can look for another possible cause and determine whether your treatment needs to be adjusted.

Be specific when describing your dizziness. For example, do you feel like the room is spinning, or do you feel lightheaded or faint? One MyBCTeam member described their dizziness this way: “The room is gently spinning, like when I used to drink too much.”

Dizziness as a Symptom of a Serious Tamoxifen Side Effect

In rare cases, dizziness can occur along with symptoms of a serious side effect of tamoxifen.

For example, tamoxifen increases the risk of blood clots. Get emergency medical help if you experience dizziness along with any symptoms that may indicate a blood clot, such as:

• Chest pain
• Shortness of breath
• Coughing up blood
• Pain or swelling in one leg

Tamoxifen also can raise the risk of stroke, which can cause the following symptoms to occur suddenly:

• Weakness or numbness in your face, arms, or legs
• Confusion
• Vision problems
• Trouble walking
• Severe headache

Call 911 or your local emergency number right away if you have symptoms of a blood clot or stroke.

Even if you don’t have emergency symptoms, talk with your doctor about dizziness that concerns you. Your healthcare team can help determine what may be causing it and how best to manage it.