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July 12, 2023 10 min read

Levothyroxine (synthetic thyroxine - T4) is the standard treatment for hypothyroidism that has helped many patients improve their symptoms and live healthier, happier lives. However, not everyone responds as well to levothyroxine as they'd hoped. Some people who take this medication still experience symptoms even though their thyroid function test results are in the normal range.

So what is the solution for them? Many experts recommend supplementing with Liothyronine (L-T3), a manmade hormone that replaces your body's natural thyroid hormone triiodothyronine (T3). The most popular brand name for liothyronine is Cytomel. But what is Cytomel? Does it have side effects? Do you need Cytomel for hypothyroidism?

In this article, we'll cover everything you need to know about Cytomel, so keep reading to find the answers to your questions!

The thyroid and its hormones

A woman dealing with hypothyroidism

First and foremost, let's talk about your thyroid. Your thyroid gland is a butterfly-shaped endocrine gland located in your neck and above your windpipe. Its function is to release two important hormones, thyroxine (T4) and triiodothyronine (T3), which regulate your metabolism, temperature, weight, and heart rate. In addition, your thyroid also releases the hormones T2, T1, and Calcitonin.

T4 and T3 are the two main hormones of the thyroid. While the T4 hormone is inactive, the T3 hormone is active and affects the functions of the body. Thus, your body needs to convert T4 to T3 in order to use it.

When you have hypothyroidism or underactive thyroid, your thyroid doesn't produce enough of its hormone. Low thyroid hormone levels slow down your metabolism, causing symptoms like brain fog, fatigue, constipation, low libido, and cold intolerance.

Therefore, if you have hypothyroidism or have an underactive thyroid gland, you don't have enough T4 and T3 in your body. As a result, you will need thyroid hormone replacement therapy, which works by replacing the thyroid hormone your body is missing.

There are different thyroid medications to treat hypothyroidism; the standard one is levothyroxine – the synthetic form of T4 that is often prescribed with brand names like Synthroid and Levoxyl. But sometimes, levothyroxine just doesn't cut it, in which case, you may need additional help. For these folks, liothyronine or natural desiccated thyroid (NDT) may be an option.

Liothyronine is the synthetic version of the active thyroid hormone T3. It's most commonly known for its brand name, Cytomel. NDT, on the other hand, contains natural forms of both T4 and T3 thyroid hormones. Some of the most well-known NDT brands are Armour Thyroid, NP Thyroid, and VitaliThy.

What is Cytomel?

Cytomel is the most common brand name for liothyronine (L-triiodothyronine or LT3). It's the manmade version of the thyroid hormone T3 in sodium salt form. It's an oral medication that comes in tablet form and is used to treat hypothyroidism by replacing the hormone that the thyroid is not producing enough of. By supplying you with T3 thyroid hormone, Cytomel can help you maintain a proper metabolic rate, so your bodily function can go back to normal.

Aside from treating hypothyroidism, Cytomel is also used as part of a thyroid suppression test for hypothyroidism. Doctors may also use Cytomel in conjunction with surgery and radioactive iodine to treat thyroid cancer. In addition, the medication is also used to treat enlarged thyroid glands and myxedema coma (severe hypothyroidism).

Since Cytomel is the synthetic version of the active thyroid hormone T3, it's often considered the most powerful thyroid medication. Moreover, it's faster than other thyroid hormone replacement therapies.

Do you need Cytomel for your hypothyroidism?

If you've been diagnosed with hypothyroidism, your doctor may prescribe levothyroxine for you. So when does Cytomel enter? Do you need it at all?

Here are some reasons why you may consider taking Cytomel:

  • You've been taking levothyroxine for a while, but your hypothyroid symptoms don't seem to improve.

  • Your thyroid tests show that you have high reverse T3 levels (RT3), which is the inactive version of the T3 thyroid hormone. High levels of RT3 usually occur when your body can't properly convert T4 to T3.

  • You have pre-diabetes, diabetes, or insulin resistance.

  • You have leptin resistance.

What are the common side effects of Cytomel?

Similar to other thyroid medicine, Cytomel may cause side effects if taken in excess. The side effects may be similar to symptoms of hyperthyroidism, such as

  • Food cravings, weight loss, excessive sweating, fever.

  • Headache, insomnia, anxiety, emotional instability.

  • Muscle cramps, tremors, or muscle weakness.

  • Tachycardia, hypertension, angina pectoris, heart failure, myocardial infarction, cardiac arrest.

  • Trouble breathing, such as shortness of breath or difficulty breathing.

  • Diarrhea, abdominal cramps, vomiting.

  • Hair loss or flushing.

  • Bone mineral density is decreased.

  • Irregular menstruation or impaired fertility.

If you are experiencing any of the side effects above, you should talk to your doctor as soon as you can. But don't worry; these symptoms are rare and usually occur because your dose is too high.

In rare cases, you might experience adverse reactions if you are allergic or hypersensitive to the binders and fillers of the medication. This may cause you to experience the following:

  • Itching, urticaria, skin rash, flushing, and angioedema.

  • Gastrointestinal symptoms, such as abdominal pain, nausea, diarrhea, etc.

  • Fever, joint pain, or wheezing.

It's important that you get immediate medical attention if you experience any of these symptoms.

Who should not use Cytomel?

Can everyone use Cytomel?

Since the thyroid hormone occurs naturally in the human body, almost anyone can take Cytomel. However, people with certain medical conditions may not be able to tolerate this medication, as well as others. If you have any of the following medications, be sure to tell your doctor.

  • Pituitary or adrenal gland problem that is not controlled by treatment.

  • Heart disease or angina (chest pain) since taking too much of this medication can cause heart problems, especially for older adults.

  • Osteoporosis or low bone mineral density since this medication may reduce calcium and other minerals in the bone. Thus, you may need to take a lower dosage of Cytomel if you already have osteoporosis.

Moreover, Cytomel shouldn't be used as a tool to help you lose weight or enhance fertility if you don't have hypothyroidism. Taking Cytomel in hopes of losing weight or treating infertility can only lead to hyperthyroidism.

How should you take Cytomel?

Unlike levothyroxine, you don't have to take levothyroxine on an empty stomach. This means that you don't necessarily have to take it first thing in the morning, at least 60 minutes before breakfast. That said, there are things you need to know to ensure that you get the most out of your meds.

  • Take your thyroid medication regularly as instructed by your doctor, even if you don't feel better.

  • If you don't feel any better, talk to your doctor about the possibility of changing your medication, stopping it, or adjusting your dose. Don't stop taking the thyroid hormone medication suddenly or change the dosage without your doctor's supervision.

  • When you're just starting Cytomel, you might need to get regular blood tests to measure how much thyroid hormone is in your system so that your doctor can find the optimal dosage of Cytomel for you. These tests will then be repeated regularly to make sure that your dose remains appropriate as time goes on.

  • Learn the ingredients of Cytomel and let your doctor know if you are allergic to any of the ingredients in the tablet.

  • Tell your doctor about all medications and herbal or vitamin supplements you are taking or plan to take. Some medications and supplements may interact with Cytomel.

  • Be honest with your doctor about other medical conditions you have, such as thyrotoxicosis, adrenal insufficiency, diabetes, high blood pressure, atherosclerosis, and angina.

  • Tell your doctor if you are going to have any surgery, including dental surgery.

  • Inform your doctor about your pregnancy plan, pregnancy, or breastfeeding.

Does Cytomel interact with other drugs?

Understanding drug interactions is important to ensure that your medication works as intended and doesn't cause any unwanted side effects. Some medications and supplements may interact with Cytomel, decreasing its absorption of the medication from the stomach and intestine into your bloodstream. Taking Cytomel at the same time as other medications may also increase your risk of side effects. This doesn't mean that you have to stop taking other medications or supplements; you just have to separate them. Take the following medications at least 4 hours apart from your Cytomel.

  • Sevelamer

  • Colestipol

  • Colesevelam

  • Cholestyramine.

The following drugs may also affect Cytomel:

  • Birth control pills

  • Antidepressant

  • Blood thinners, such as Coumadin, Jantoven, and Warfarin

  • Oral diabetes medicine or insulin

  • Steroid medicine

  • Cold or cough medicine

  • Cancer medicine

  • Seizure medicine.

Keep in mind that the above list is not exhaustive. Thus, you should tell your doctor about all the medicines you're currently taking.

Can you use Cytomel in combination with levothyroxine?

Can you combine Cytomel with levothyroxine?

Combining liothyronine and levothyroxine is somewhat controversial. The American Thyroid Association guidelines don't recommend the two medications together. However, Cytomel (liothyronine) and Synthroid (levothyroxine) are often used in conjunction, especially for those whose hypothyroidism symptoms don't improve with levothyroxine alone.

Various studies found that adding liothyronine like Cytomel to levothyroxine may improve energy, mood, and concentration. Many patients also claim that they prefer the combination of the two more than taking just one.

Keep in mind that adding liothyronine with levothyroxine is an important decision that should be supervised by a doctor.

How much Cytomel should you take?

The recommended dose of Cytomel depends on the age, weight, specific medical condition, the reason for taking it, and lab results of each person. Therefore, keep in mind that the following information are only the average doses of Cytomel.

1. For hypothyroidism treatment

For adults, the recommended initial dose of Cytomel is 25 mcg per day. After 1 to 2 weeks, this dose can be increased further if needed. Maintenance average doses are usually in the range of 25 mcg to 75 mcg per day.

Older adults and people with heart disease usually need lower doses of Cytomel, usually starting from 5 mcg per day. This dosage can be gradually increased over a recommended period.

For children, experts recommend an initial daily dose of 5 mcg. The dose can then be doubled every 3 or 4 days until the right dose is reached.

2. For cancer treatment

Cytomel is used to inhibit thyroid-stimulating hormone (TSH) in thyroid cancer. The specific dosage of Cytomel depends on the expected TSH level that your doctor expects.

3. For the diagnosis of thyroid problems

Cytomel is often used in thyroid suppression tests. In this case, a higher dosage might be needed, usually around 75 to 100 mcg once daily for 7 days.

What happens if you take too much Cytomel?

As you know, if you have an underactive thyroid function, you have hypothyroidism and don't have enough thyroid hormone in your body. The most common treatment is thyroid hormone replacement medication.

However, if you take too much thyroid hormone, you have hyperthyroidism with symptoms like headaches, nervousness, insomnia, irregular periods, appetite, weight loss, diarrhea, etc.

More serious symptoms are shortness of breath, heart attack, tremors, muscle weakness, etc. In addition, several reports of convulsions, cerebral embolism, shock, coma, and death have occurred.

These symptoms are not always obvious. They may not even appear until a few days after an overdose. Therefore, if you have the symptoms of overdose listed, you should see your doctor for a temporary reduction or temporary cessation of your dose of Cytomel and help in treating your medical condition. In the event of an emergency, call the Poison Control center at (800) 222-1222 if you live in the United States.

In contrast, what happens if you miss a dose of Cytomel? In fact, if you miss a dose within an hour, you can take Cytomel right away, and remember to keep taking it regularly for the following days. However, you can consult your doctor if you have missed a dose within 12 hours. Usually, doctors will let you skip the missed dose.

Is it okay to take Cytomel while you're pregnant or breastfeeding?

A woman with her baby.

If you're planning to get pregnant and you're currently taking Cytomel for your hypothyroidism, it's understandable to have concerns about how the thyroid hormone medication may affect your unborn baby. But the truth is, untreated hypothyroidism during pregnancy poses a greater risk to both your and your little one's health.

Untreated hypothyroidism can lead to potential complications such as gestational hypertension and premature birth. Additionally, it can negatively impact your baby's neurocognitive development. That's why it's crucial to maintain optimal thyroid hormone levels during pregnancy, meaning you should continue taking Cytomel.

Your doctor may adjust your dosage during each trimester and may even increase it from your pre-pregnancy levels. To ensure everything is going well, your doctor will also check your TSH levels regularly. After giving birth, your hormone levels will be adjusted back to normal.

And the good news is Cytomel is safe for unborn babies. The thyroid hormone hardly crosses the placenta and poses no adverse effects on the mother or baby.

In terms of breastfeeding, research has shown that there is no significant difference in the blood levels of the hormones T4 and T3 in breastfed and bottle-fed infants.

The study shows that the T3 hormone passes from the blood into breast milk in a very small amount, only about 5 to 1000 ng per day, so it doesn't affect the baby's pituitary axis. Moreover, T4 was not detected in breast milk samples.

Does Cytomel work right away?

Cytomel begins working quickly - within just a few hours of taking it. In fact, up to 95% of the dose is absorbed within 4 hours. However, it may take around 2 to 3 days for you to start noticing improvements in your symptoms.

What are the alternatives to Cytomel?

A woman taking natural desiccated thyroid (NDT)

If you're thinking about adding T3 into your treatment and combining it with levothyroxine, there are other options you can consider: natural desiccated thyroid (NDT). Extracted from dried pig thyroid glands, it's a more natural option that mimics the thyroid hormone that occurs naturally in the human thyroid gland. It contains not only T4 and T3, the two main thyroid hormones, but also T2, T1, and Calcitonin.

T2 is believed to help with insulin resistance and fat metabolism, while Calcitonin promotes bone density. This unique combination of hormones brings a more comprehensive approach to balancing your body's needs.

Due to its complex composition, NDT is a popular choice among patients who have not found success with T4-only and T3-only medications. One great brand you can consider is VitaliThy, a natural desiccated thyroid you can buy online. Aside from having all the hormones that naturally occur in your thyroid gland, it's also gluten- and lactose-free. Plus, it doesn't contain any shellfish, fish, or eggs, as well as artificial coloring and flavoring. Thus, it's a truly natural option for those looking for the best thyroid hormone replacement.

Wojciech Majda
Wojciech Majda

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