Effects of Carnitine on Thyroid Health

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Discovered many years ago, carnitine has earned a lot of respect since its initial discovery, with more and more beneficial effects being added to the already long list that exists.

Today, while we will also list some of the most influential effects and functions of carnitine in the human body, we will focus on its function regarding our thyroid health.

Can carnitine be used in the battle against the common thyroid disorders?

What is carnitine?

Carnitine is a water-soluble amino acid found in every cell in the human body. There are three different forms of this popular amino acid – L-carnitine, propionyl-L-carnitine, and acetyl-L-carnitine, with L-carnitine being the most popular one of the three.

Each of these three forms has a specifically important function in the human body.

For example, while L-carnitine is most beneficial for our muscles, acetyl-L-carnitine is most beneficial for our brain, whereas propionyl-L-carnitine is closely related to the blood circulation in the body.

Since it was first isolated from meat, this amino acid has been given the name that reminds us of the Latin word for flesh – carnus.

The primary method of introducing carnitine to our body is by eating meat, which is later stored within the skeletal and cardiac muscle tissue. But carnitine is also produced by the human body, specifically by the liver and kidneys.

Two amino acids are used in the production of carnitine – lysine, and methionine.

What does carnitine do in the human body?

Carnitine, with each and every one of its different forms, is one of the most valuable amino acids in the human body. This is one of the many reasons why its popularity has been growing so rapidly in the last couple of years.

What will follow are some of the biggest reasons why more and more people are getting interested in this important amino acid.

A valuable agent in energy production in the body

One of the primary roles of carnitine in the human body is being a part of the energy production process that is happening within our body’s powerhouses – the mitochondria. One part of carnitine has a role in transporting the long-chain fatty acids inside the mitochondria.[i] Once this part of the energy production process has been completed, the mitochondria then proceed to oxidize these fatty acids in order to produce the much-needed energy throughout the day, especially the skeletal and heart muscles which use fatty acids as their primary source of fuel.

A powerful antioxidant

The everyday processes that are happening inside our body in order to help us function properly result in waste and toxic compounds that need to be eliminated as soon as possible.

If their levels grow in the body, the levels of oxidative stress grow as well, thus exposing us to many health risks such as heart disease, high blood pressure, diabetes, cancer, etc.

This is where the powerful antioxidants such as carnitine come in handy[ii]

A weight-loss assistant

Since carnitine helps transport fatty acids and use them as an energy source, it is expected that carnitine would also help increase the burning of fats, thus inducing weight loss.

That is, after all, the effect that you are trying to achieve by keeping to a calorie deficit and working out in order to burn more fats. L-carnitine seems to be especially beneficial in this case. A 2005 study support this, showing that L-carnitine can help burn more fat when combined with a 90-minute stationary bicycle workout.[iii]

A supporting agent in the healthy aging process

It has been suggested that carnitine can support a healthy aging process. The reason for that is the fact that with the normal aging process, the mitochondrial function declines, mainly because of the decline in carnitine’s production.

Science has shown that supplementing with carnitine, especially with acetyl-L-carnitine, can support a healthy aging process.[iv]

A heart health and insulin resistance-friendly agent

Because of its strong antioxidant abilities, carnitine, especially L-carnitine, has been widely used to support a healthy heart function, with a special focus on patients with a history of heart disease.

Multiple studies have shown that when used, L-carnitine can help reduce the high blood pressure, which along with oxidative stress, serves as one of the main risk factors for heart disease, thus reducing the risk of this horrifying disease and improving the patients’ heart health.[v]

But that is not all since carnitine is also able to improve insulin resistance, thus maintaining good control over the blood sugar levels. High blood sugar levels are yet another risk factor that threatens our health, which is why it is a good thing to have something as strong as carnitine to lean on for support.

Carnitine sources that you need to know about

We mentioned carnitine is produced in the human body daily, thanks to the hard-working liver and kidneys. In a healthy individual, his/her liver and kidneys usually produce enough carnitine, and there is rarely a need for a healthy individual to use food sources or various supplementation to help satisfy the supposed daily requirements.

However, sometimes, due to a genetic or a medical reason, your body may not be able to produce enough carnitine. When the body is producing too little carnitine, the individual is exposed to the risk of carnitine deficiency.

This condition, if left untreated, can be potentially fatal. In this case, pharmaceutical carnitine is prescribed, along with a diet that will include more of the usual carnitine food sources.

If you go back to the beginning of today’s article, you will remind yourself that carnitine was first isolated from meat. Animal products, especially meat, contain high levels of carnitine. Among the best carnitine sources out there, we have beef, milk, chicken breast, and cheese, especially cheddar. Whole-wheat bread and asparagus also contain high levels of carnitine as well.

And if you are interested in supplementing with carnitine, you will be surprised to find out how many different brands are offering their version of carnitine supplements. Especially popular seems to be the L-carnitine supplement, widely used by athletes around the world, looking for something that will help them to enhance their physical performance. Older adults are also recommended to include a proper L-carnitine supplement in their diet, as vegans and vegetarians are because of their diet that lacks the biggest carnitine natural sources.

Although generally considered to be safe, any use of carnitine supplements needs to be limited to no more than 3 grams per day. According to the National Institutes of Health (NIH), anything above this limit can cause nausea, vomiting, and abdominal cramps.[vi]

Can carnitine enhance your thyroid health?

Since carnitine is closely involved with the mitochondria, which on the other hand, are linked to our metabolic health, it only makes sense to look into the carnitine levels within patients struggling with metabolic disorders, such as thyroid disorders.

The first thyroid disorder that was looked at was Grave’s disease. As you may now, Grave’s disease is one of the most common causes of hyperthyroidism – a condition in which the thyroid gland is overproducing the two thyroid hormones.

To investigate the effects of carnitine on thyroid health, researchers measured the carnitine levels within Grave’s disease patients.

What their research showed was low carnitine levels in comparison to the high thyroid hormone levels, with higher levels of carnitine being excreted in the urine. They got the idea to use carnitine supplementation to lower the thyroid hormone levels because of the ability of carnitine, especially L-carnitine, to prevent the thyroid hormones from entering the blood flow.

When women struggling with hyperthyroidism due to Grave’s disease were given L-carnitine supplements, they experienced an improvement in their hyperthyroidism symptoms. The symptoms were successfully reversed, and the overall health of the patients was improved.[vii]

Speaking of hypothyroidism, another common thyroid disorder, which, unlike hyperthyroidism, characterizes itself with lower than normal thyroid hormone levels – carnitine has also promoted an improvement in its symptoms.

What many people do not know is while hypothyroidism is controlled efficiently with the use of levothyroxine – a synthetic version of thyroxine, levothyroxine also causes carnitine synthesis. Now you would think that this is a good thing, but know this – while more carnitine is being produced, the increased thyroxine levels also lead to an accelerated mitochondrial fatty acid oxidation, which causes the carnitine levels to drop.

While this may not be a problem for most hypothyroidism patients, it will be a problem for those who are already struggling with a carnitine deficiency. This is one of the many cases where a quality carnitine supplement would come in handy, considering the extreme fatigue that carnitine deficiency can lead to.

But fatigue is also a big problem for hypothyroidism patients in general, even when a carnitine deficiency is not a question. Luckily for these patients, proper carnitine supplementation has been shown quite the satisfying results regarding not only fatigue but also muscle weakness, which is yet another common symptom due to hypothyroidism.[viii]

Muscle weakness and pain are seen in both hypo- and hyperthyroidism, which is why carnitine supplements are commonly recommended to these two groups of patients. The symptoms are especially present in hypothyroidism patients, who tend to have lower than normal muscle carnitine levels, which are to be blamed for these common symptoms.[ix] But as the results of this and many other studies suggest, carnitine can easily prevent and reduce any present muscle weakness and pain, thus improving the patient’s quality of life.

Despite all of its beneficial effects, hypothyroidism patients need to use carnitine supplements with a high dose of caution. These supplements are only to be used upon a doctor’s recommendation, and its recommended dosage is to be strongly respected. That includes paying attention when including the known animal and plant carnitine sources, which we mentioned earlier.

The reason why we are telling you this is because of the ability of carnitine to inhibit and prevent the thyroid hormones from entering the blood flow, thus reducing the already low thyroid hormone levels. Although this is a much-needed effect in hyperthyroidism patients, it is a different story, in regards to hypothyroidism patients.


Carninte’s primary function to help energize the body, especially the skeletal and cardiac muscles where it is stored.

Carnitine can help us protect our thyroid health, and when paired with the proper medication.

Consult your doctor about the possibility of including a quality carnitine supplement.


[i] Foster, D. W. (2004). The Role of the Carnitine System in Human Metabolism. Annals of the New York Academy of Sciences1033(1), 1–16. doi: 10.1196/annals.1320.001
Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/15590999

[ii] Solarska, K., Lewińska, A., Karowicz-Bilińska, A., & Bartosz, G. (2010). The antioxidant properties of carnitine in vitro. Cellular and Molecular Biology Letters15(1). doi: 10.2478/s11658-009-0036-y
Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6275708/

[iii] Broad, E. M., Maughan, R. J., & Galloway, S. D. (2005). Effects of Four Weeks L-Carnitine L-tartrate Ingestion on Substrate Utilization during Prolonged Exercise. International Journal of Sport Nutrition and Exercise Metabolism15(6), 665–679. doi: 10.1123/ijsnem.15.6.665
Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/16521850

[iv] Montgomery, S. A., Thal, L., & Amrein, R. (2003). Meta-analysis of double-blind, randomized controlled clinical trials of acetyl-L-carnitine versus placebo in the treatment of mild cognitive impairment and mild Alzheimer’s disease. International Clinical Psychopharmacology18(2), 61–71. doi: 10.1097/00004850-200303000-00001
Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/12598816?dopt=Abstract

[v] Ruggenenti, P., Cattaneo, D., Loriga, G., Ledda, F., Motterlini, N., Gherardi, G., … Remuzzi, G. (2009). Ameliorating Hypertension and Insulin Resistance in Subjects at Increased Cardiovascular Risk: effects of acetyl-L-carnitine therapy. Hypertension54(3), 567–574. doi: 10.1161/hypertensionaha.109.132522
Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/19620516

[vi] Office of Dietary Supplements – Carnitine. (n.d.).
Retrieved from https://ods.od.nih.gov/factsheets/Carnitine-HealthProfessional/

[vii] Benvenga, S., Ruggeri, R. M., Russo, A., Lapa, D., Campenni, A., & Trimarchi, F. (2001). Usefulness ofl-Carnitine, A Naturally Occurring Peripheral Antagonist of Thyroid Hormone Action, in Iatrogenic Hyperthyroidism: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial. The Journal of Clinical Endocrinology & Metabolism86(8), 3579–3594. doi: 10.1210/jcem.86.8.7747
Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/11502782

[viii] Benvenga, S., Feldt-Rasmussen, U., Bonofiglio, D., & Asamoah, E. (2019). Nutraceutical Supplements in the Thyroid Setting: Health Benefits beyond Basic Nutrition. Nutrients11(9), 2214. doi: 10.3390/nu11092214
Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/31540254

[ix] Sinclair, C., Gilchrist, J. M., Hennessey, J. V., & Kandula, M. (2005). Muscle carnitine in hypo- and hyperthyroidism. Muscle & Nerve32(3), 357–359. doi: 10.1002/mus.20336
Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/15803480

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