Lo Loestrin Fe (norethindrone/ethinyl estradiol/ferrous fumarate) is a prescription drug used to help prevent pregnancy. Lo Loestrin Fe can cause side effects that range from mild to serious. Examples are headache and nausea.

Specifically, Lo Loestrin Fe is used to help prevent pregnancy in females of any age who are able to become pregnant. (Here, we use the term “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.)

Lo Loestrin Fe may not be effective for individuals with a body mass index (BMI) greater than 35 kilograms per meter squared (kg/m2).

The drug comes as oral tablets. Be sure to keep this pill pack out of the reach of children to avoid accidental iron and other poisoning.

Lo Loestrin Fe has three types of tablets. The active ingredients in each are:

  • Active tablets (24): norethindrone acetate and ethinyl estradiol
  • Active tablets (2): ethinyl estradiol
  • Inactive tablets (2): ferrous fumarate (iron)

Keep reading to learn about common, mild, and serious side effects that Lo Loestrin Fe can cause. For a general overview of the drug, including details about its uses, see this article.

Lo Loestrin Fe has a boxed warning. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Side effects explained” section.

Some people may experience mild to serious side effects during their Lo Loestrin Fe treatment. Examples of the drug’s commonly reported side effects include:

  • headache
  • vaginal bleeding or spotting between periods
  • nausea and vomiting
  • painful period
  • weight gain

The following sections include more side effects of Lo Loestrin Fe. Each person’s experience with side effects may differ.

Mild side effects have been reported with Lo Loestrin Fe. These include:

  • acne
  • decreased sex drive
  • bloating or fluid retention
  • breast soreness
  • weight gain
  • painful period
  • vaginal bleeding or spotting between periods
  • headache
  • nausea and vomiting
  • uneven dark spots on the skin, especially the face

In most cases, these side effects should be temporary. And some may be managed easily. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop taking Lo Loestrin Fe unless your doctor recommends it.

Lo Loestrin Fe may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

Serious side effects have been reported with Lo Loestrin Fe. These include:

If you develop serious side effects while taking Lo Loestrin Fe, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911. Or call your local emergency number.

Learn more about these side effects in the “Side effects explained” section:

  • serious migraine
  • increased risk of breast cancer
  • boxed warning: cigarette smoking and increased serious CV events

Note: After the FDA approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Lo Loestrin Fe, visit MedWatch.

Allergic reaction

For some people, Lo Loestrin Fe can cause an allergic reaction. But this side effect wasn’t reported in the drug’s studies.

In general, symptoms of allergic reaction can be mild or serious.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. They also can determine whether you should continue Lo Loestrin Fe treatment.

If you have symptoms of a severe allergic reaction, such as swelling or difficulty breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

Your doctor can confirm whether you’ve had a serious allergic reaction to Lo Loestrin Fe. If so, they may have you switch to a different treatment.

Get answers to some frequently asked questions about Lo Loestrin Fe’s side effects.

What side effects may occur in the first month of taking Lo Loestrin Fe?

It’s common to have the following side effects during the first few months of Lo Loestrin Fe treatment:

  • spotting or light bleeding between periods
  • nausea
  • vomiting

To help with nausea, take Lo Loestrin Fe with food or at bedtime.

As your body gets used to the medication, these side effects will go away. Talk with your doctor right away if unusual bleeding is excessive. And also let them know right away if you’re not able to keep down Lo Loestrin Fe tablets.

Can Lo Loestrin Fe cause me to gain weight?

Studies found that weight gain while taking Lo Loestrin Fe was an uncommon side effect. They also found that it may be related to fluid retention during your monthly menstrual cycle.

If you are concerned about weight gain, check with your doctor or pharmacist. They may have suggestions for managing your weight during Lo Loestrin Fe treatment.

What are the side effects of Lo Loestrin Fe in persons over age 40 years?

Generally, side effects of Lo Loestrin Fe are the same in people over age 40 years and people who are younger. But some side effects have a higher risk as age increases.

Examples are:

If you are over age 40 years, discuss these risk factors with your doctor or pharmacist. Likewise, regular medical check-ups can help you stay updated on new recommendations for your age and risk factors.

Learn more about some of the side effects Lo Loestrin Fe may cause.

Boxed warning: Risk of cigarette smoking and increased serious CV events

Lo Loestrin Fe has a boxed warning for the risk of cigarette smoking and increased serious CV events. (CV relates to the heart and blood vessels.)

The risk of serious CV events with cigarette smoking was a common side effect reported in studies. These studies examined combination oral contraceptives (COCs) such as Lo Loestrin Fe.

The first year of taking a COC poses the greatest risk. This risk rises as both the number of cigarettes smoked and your age increase. If you are over age 35 years and smoke, you should avoid taking COCs.

Serious CV events include:

Other factors that can increase the risk of serious CV events when taking this drug include:

What might help

If you have a risk of serious CV events during Lo Loestrin Fe treatment, consider:

  • stopping smoking, if you smoke
  • exercising regularly
  • maintaining a healthy weight
  • eating a nutritious diet low in saturated fat
  • keeping blood pressure, blood sugar, and cholesterol in check
  • asking your doctor about nonhormonal contraceptives

If you have concerns about your CV risks, check with your pharmacist or doctor.

Increased risk of breast cancer

An increased risk of breast cancer was an uncommon side effect reported in studies of Lo Loestrin Fe. Some studies, though not all, suggest a slight increase in breast cancer risk for current long-term COC users.

Breast cancer may cause symptoms such as:

  • swelling or lump in the breast or under the arm
  • nipple changes, rash, or discharge
  • changes in the shape of the breast
  • changes in the feel or look of the breast skin
  • breast or underarm pain not related to your period

Factors that can increase the risk of breast cancer when taking this drug include:

  • family history of breast cancer, such as in mother, daughter, or sister
  • taking COCs at a young age and continuing for many years
  • smoking or excessive alcohol use
  • inactive lifestyle
  • BMI equal to or greater than 30 kg/m2

What might help

Scheduling a yearly wellness visit with your doctor is essential for breast cancer prevention. And practicing monthly self-exams can help you find breast changes earlier.

If you have concerns about developing breast cancer while taking Lo Loestrin Fe, talk with your doctor or pharmacist.

Serious migraine

Serious migraine was an uncommon side effect reported in studies of Lo Loestrin Fe. Serious migraine may cause symptoms such as:

  • nausea and vomiting
  • fatigue (low energy)
  • severe piercing pain on one side of the head
  • sensitivity to light or sound
  • neck pain or stiffness

If you experience migraine with aura during Lo Loestrin Fe treatment, be cautious. This may be a sign of a possible stroke and may require emergency medical treatment. Symptoms of aura include:

  • visual problems, such as flashing lights or spots in your vision
  • difficulty speaking
  • tingling or numbness in the face, arms, or legs

Factors that can increase the risk of serious migraine when taking this drug include:

  • history of migraine
  • BMI equal to or greater than 30 kg/m2
  • smoking
  • excessive alcohol or caffeine use
  • poor sleep habits
  • high blood pressure

What might help

If you are concerned about having severe migraine during Lo Loestrin Fe treatment, try these suggestions:

  • eat a healthy diet and drink plenty of water
  • stop smoking
  • exercise
  • avoid excessive alcohol or caffeine
  • create a good sleep routine

You also may want to talk with your doctor or pharmacist about your risk factors for severe migraine. They can help you decide whether Lo Loestrin Fe is right for you.

Keeping track of side effects

During your Lo Loestrin Fe treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking a new drug or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Sharing notes with your doctor will help them learn more about how Lo Loestrin Fe affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before taking Lo Loestrin Fe.

Boxed warning: Risk of cigarette smoking and increased serious CV events

Lo Loestrin Fe has a boxed warning for the risk of cigarette smoking and increased serious CV events. A boxed warning is the most serious warning from the FDA. For details, see the “Side effects explained” section earlier in this article.

Other warnings

Lo Loestrin Fe can sometimes cause harmful effects in people who have certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Lo Loestrin Fe is a good treatment option for you.

Talk with your doctor about your health history before you take Lo Loestrin Fe. Be sure to tell them whether any of the following factors apply to you:

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 another 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.