Forteo (teriparatide) is a brand-name subcutaneous injection pen that’s prescribed for certain types of osteoporosis. As with other drugs, Forteo can cause side effects, such as joint pain.

Forteo belongs to a drug class called parathyroid hormone analogs. The drug is available in a generic version.

Read on to learn about potential common, mild, and serious side effects of Forteo. For a general overview of the drug, including details about its uses, see this article.

Forteo can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Forteo in clinical trials:

* For more information about this side effect, see “Side effect specifics” below.

Mild side effects can occur with Forteo use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to Forteo’s prescribing information.

Mild side effects that have been reported with Forteo include:

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking Forteo and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

Forteo may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to Forteo’s prescribing information.

If you develop serious side effects while taking Forteo, 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 your local emergency number.

Serious side effects that have been reported include:

* For more information about this side effect, see “Side effect specifics” below.
† An allergic reaction is possible after administering Forteo. However, it’s not clear whether this side effect occurred in clinical trials. To learn more, see the “Side effect specifics” section below.

Forteo may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Does Forteo cause teeth-related side effects?

A small percentage of people who took Forteo in clinical trials reported a tooth disorder. The drug’s manufacturer didn’t include details about these reported tooth-related side effects.

If you’re having tooth pain or other tooth-related problems, contact your doctor or dentist as soon as possible. They can determine whether your symptoms are related to Forteo.

Is weight gain or weight loss a side effect of Forteo?

You shouldn’t have weight gain or weight loss as a side effect of Forteo. People taking Forteo in clinical trials didn’t report either of these side effects.

However, weight loss can be a symptom of a high calcium level. This is a rare, serious side effect of Forteo. You can read more about this side effect in the “Side effects specifics” section below.

If you notice changes in your weight during treatment with Forteo, talk with your doctor. They can determine the most likely cause of your weight changes and suggest ways to manage it.

Can Forteo cause long-term side effects?

Long-term treatment with Forteo can increase the risk of certain long-term side effects, such as osteosarcoma. You can read more about these side effects below in the “Side effects specifics” section.

Ask your doctor how long you can expect to need Forteo treatment and the risks of long-term treatment.

Will I experience hair loss during Forteo treatment?

You shouldn’t experience hair loss as a side effect of Forteo. Hair loss wasn’t reported in clinical trials of the drug.

Keep in mind that doctors prescribe Forteo for certain types of osteoporosis. Hormonal changes, such as a loss of estrogen or testosterone, often contribute to osteoporosis. The loss of these hormones can also cause other changes, such as hair loss.

Talk with your doctor if you notice hair loss. They can determine the most likely cause and suggest ways to manage it.

Learn more about some of the side effects that Forteo may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Forteo.

Osteosarcoma (a form of bone cancer)

It’s possible that Forteo could increase the risk of osteosarcoma. This risk was reported in animal studies of Forteo. However, animal studies don’t always predict what will happen in humans.

In human clinical trials of Forteo, there hasn’t been an increased risk of osteosarcoma. However, people in these trials only had treatment with Forteo for 2 years. There isn’t enough information to know whether the risk is higher after 2 years of treatment with the drug.

In addition, certain people may have a higher risk of developing osteosarcoma. This includes people who have already had bone cancer and people with bone diseases, such as Paget’s disease.

Symptoms of osteosarcoma can include:

  • bone pain
  • limited range of motion in a joint
  • pain when you put weight on a bone
  • swelling
  • discoloration of the affected area

What you can do

To help avoid this risk, doctors typically don’t prescribe Forteo for longer than 2 years. Talk with your doctor about your risk of osteosarcoma and find out how long you’ll need to take Forteo. If you have bone disease or have had bone cancer, tell your doctor before starting Forteo. They may recommend a treatment other than Forteo to decrease your risk of developing osteosarcoma.

High level of calcium in the blood or body tissues

It’s possible that Forteo may cause a high level of calcium in the blood. Symptoms can include:

Forteo may also cause calcium deposits in the skin or small blood vessels in the fat and skin. This can cause painful skin lesions and skin ulcers. People who take certain medications or have kidney problems or autoimmune diseases may have a higher risk.

What you can do

Tell your doctor if you develop symptoms of a high calcium level or have problems with your skin. They may suggest stopping Forteo and starting a different treatment.

Orthostatic hypotension

Orthostatic hypotension is a sudden drop in blood pressure when you change positions. It can happen when you stand up quickly from a seated or lying down position. It’s typically mild and only causes brief dizziness or lightheadedness. However, it can cause fainting and falls, which can be serious.

What you can do

Orthostatic hypotension is most common with the first few doses of Forteo. It’s a good idea to take your Forteo doses in a place where you can sit or lie down if you start to feel dizzy or lightheaded.

Your body should get used to Forteo, and this effect should go away with time. If it persists or causes you to faint or fall, let your doctor know. They may suggest changes to your treatment plan.

Joint pain

Joint pain and general body pain are common side effects of Forteo. In most cases, this side effect isn’t serious. However, joint pain or bone pain can be symptoms of osteosarcoma (a form of bone cancer). You can read more about osteosarcoma above.

What you can do

Tell your doctor about any joint or bone pain that you have. They can determine the most likely cause and suggest ways to manage it.

Allergic reaction

As with most drugs, Forteo can cause an allergic reaction in some people. However, it’s not clear whether this side effect occurred in clinical trials.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Forteo. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Be sure to talk with your doctor about your health history before starting treatment with Forteo. This drug may not be the right treatment option for you if you have certain medical conditions or other factors that affect your health. These are known as drug-condition or drug-factor interactions. The conditions and factors to consider include:

Allergic reaction. If you’ve had an allergic reaction to Forteo or any of its ingredients, your doctor will likely not prescribe Forteo. Ask your doctor what other medications may be better options for you.

Autoimmune diseases. People with autoimmune diseases, such as multiple sclerosis, are more likely to have problems with calcium skin deposits during Forteo treatment. Symptoms can include skin lesions, skin discoloration, open sores, or ulcers. Tell your doctor if you have an autoimmune disease and ask whether Forteo is right for you.

Bone conditions. People with certain bone conditions have a higher risk of developing osteosarcoma (a form of bone cancer). Taking Forteo may increase this risk even more. Tell your doctor if you have a bone disease, a history of bone cancer, or a hereditary condition that increases your risk of osteosarcoma. Also, let your doctor know if you’ve had any type of radiation to your skeleton. They can determine whether Forteo is the right choice for you.

Taking digoxin. Forteo can cause a temporary increase in calcium level. This can cause problems in people taking digoxin. A high level of calcium with digoxin is believed to increase the risk of ischemic myocardial contracture (also known as “stone heart” syndrome). This is a rare condition that causes the muscles of the heart to harden and not be able to pump blood throughout the body. Tell your doctor if you take digoxin and ask about your treatment options.

High calcium problems, including hyperparathyroidism. Forteo may worsen high calcium problems in people who’ve had high blood calcium or skin calcifications in the past. This includes people with hyperparathyroidism (high parathyroid hormone). If you have or have had high calcium problems, your doctor will most likely recommend another treatment for your condition.

Kidney problems. Forteo hasn’t been clinically trialed in people with severe kidney problems. People with kidney failure have a higher risk of calcium skin deposits while taking Forteo. Tell your doctor if you have kidney problems. They may recommend a different treatment option for you.

Bladder or kidney stones. It’s possible that Forteo may increase the level of calcium in your urine. This can increase your risk of bladder or kidney stones. If you already get bladder or kidney stones, Forteo may worsen your condition. Talk with your doctor if you have had bladder or kidney stones before starting Forteo. They will monitor you more closely during treatment or they may suggest a different treatment option for you.

Taking warfarin or corticosteroids. Talk with your doctor if you are taking warfarin or corticosteroids. Skin calcifications may be more likely to occur or worsen if you take these drugs in combination with Forteo. Tell your doctor about all your medications before starting treatment with Forteo. They can determine the best treatment for your condition.

Alcohol with Forteo

There are no known interactions between alcohol and Forteo. However, alcohol can cause some of the same side effects as Forteo, such as dizziness, nausea, and orthostatic hypotension. Combining Forteo and alcohol may make these side effects worse.

In addition, long-term or excessive alcohol consumption can have negative effects on your bone health. Keep in mind that doctors prescribe Forteo for certain types of osteoporosis. So drinking alcohol may interfere with your treatment.

If you have questions about drinking alcohol during Forteo treatment, talk with your doctor or pharmacist.

Pregnancy and breastfeeding during Forteo treatment

It isn’t known whether Forteo is safe to administer during pregnancy or while breastfeeding. The drug’s manufacturer recommends avoiding Forteo in both situations.

In animal studies, treatment with Forteo at very high doses resulted in possible congenital anomalies (commonly known as birth defects) and growth development issues. Forteo has not been clinically trialed in pregnant or breastfeeding people.

Keep in mind that doctors commonly prescribe Forteo for osteoporosis that occurs after a person’s reproductive age. However, if you become pregnant while taking Forteo, let your doctor know right away. They’ll likely recommend stopping the drug.

If you’re pregnant, talk with your doctor before starting Forteo. You should also talk with them if you’re breastfeeding. Your doctor can help determine whether Forteo is the right treatment option for you.

Forteo has some common side effects that are typically mild. However, serious side effects are possible. If you’d like to learn more about Forteo, talk with your doctor or pharmacist. They can help answer any questions you have about side effects from taking the drug.

Besides talking with your doctor, you can do some research on your own. These articles might help:

  • More information about Forteo. For details about other aspects of Forteo, refer to this article.
  • Drug comparison. To learn how Forteo compares with Tymlos, read this article.
  • A look at osteoporosis. For details about osteoporosis, see our list of osteoporosis articles.

Disclaimer: Medical News Today 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.