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What are L-Arginine Side Effects?

By Vasanth S.
Updated Mar 03, 2024
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The primary side effects of L-arginine are gastrointestinal, and include mild abdominal cramps, diarrhea, and bloating. In most people these go away after a few days, usually once the body gets used to the supplementation; pain that is extreme or that doesn’t improve may be a sign that the dosage is too high, and may also signal a sensitivity or allergy. L-arginine can also cause blood pressure fluctuations, which can be particularly problematic for people who have naturally low blood pressure, those who are taking regulatory medication, and people preparing for surgery. Inflammation of the joints, particularly gout, has been documented as well, and those who have been infected with the herpes virus often see flare-ups when using this supplement. Even though the compound is natural, it isn’t always safe for everyone. Side effects are normally mild, but not always. Most health experts recommend that anyone interested in this or other supplements talk to a doctor, nurse, or pharmacist first, and take it only under supervision.

Protein Basics

L-arginine is one of the building blocks of protein. It is an amino acid that is found in a variety of foods including chicken, fish and dairy products. Many people take L-arginine as a supplement to treat certain medical conditions, including congestive heart failure and bladder inflammation.

The body needs the L-arginine compound for a number of important functions. For example, it stimulates the release of certain chemicals in the body, including insulin and growth hormone. It also helps remove ammonia from the body and aids in the wound healing process, and is an essential part of the creatine creation process. Creatine supplies muscles with energy. Additionally, the breakdown of L-arginine produces nitric oxide, which widens blood vessels and improves blood flow.

Understanding Supplementation

Healthy people typically produce all the L-arginine they need naturally. Supplementation is usually only recommended when the body can't produce enough of the substance on its own, and side effects typically only happen in the case of supplementation. Medical conditions that can lead to a L-arginine deficiency include malnourishment, severe burns, infections, high levels of ammonia in the blood, and problems with urea production. Symptoms associated with L-arginine deficiency include hair loss, skin rashes and poor wound healing.

The compound is usually available as a prescription drug supplement, but in some places it may also be available over the counter. Medical experts usually advise that dosage be calculated based both on a person’s condition as well as his or her individual circumstances, including how much, if any, the body is producing naturally.

Gastrointestinal Issues

The most common side effects are digestive; people often feel tightness in their stomach and may experience gas and bloating. Diarrhea and loose or watery stools are also common, and can last for the first days and weeks of supplementation.

Blood Pressure Drops

Blood pressure can also be affected by L-arginine, which may be a concern for those taking blood pressure medications or undergoing surgery. L-arginine can enhance the effect of medications designed to lower blood pressure, causing blood pressure to drop lower than expected, leading to dizziness and fainting. Individuals with naturally low blood pressure may also experience these symptoms. During surgery, normal blood pressure control could also be affected by the protein compound, which may lead to complications.

Who is Most at Risk

L-arginine side effects tend to be the most pronounced in those who are allergic to the compound. Allergic reactions are rare, but possible. Asthma and swelling of the airways are generally the most common signs of a reaction. Even discounting allergies, some people are more prone to negative reactions than others. Children and pregnant women, for instance, are typically more likely to experience L-arginine side effects, especially when the dosage is high.

Weighing the Pros and Cons

People deciding whether supplementation is right for them are usually wise to consider the benefits as well as the possible side effects. Even when L-arginine is present in normal amounts, supplementation may have some benefits for existing medical conditions. For example, the wound healing properties of L-arginine can speed up the healing process after surgery. The compound can also reduce the chest pain and fluid accumulation associated with congestive heart failure, and in some cases has been used to help improve erectile dysfunction by improving blood flow. When taken in combination with hydroxymethylbutyrate and glutamine, L-arginine can help increase weight and strengthen the immune system for patients suffering from wasting diseases.

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Discussion Comments
By Majorkir — On May 12, 2013

I took L-Arginine for a heart condition and the results were amazing. My blood pressure normalised and my cholesterol lowered and I felt I had tonnes more energy. This apparently was due to increased Nitric Oxide production in my arteries.

What I learned from my research is not all L-Arginine is the same, and the source is very important. It's worth paying more and make sure it comes from a vegetable source and not from beef or fish which are acidic. Thanks to L-Arginine I was able to get off statins, which were causing me real problems

By anon271101 — On May 25, 2012

I started taking l-arginine six times daily to help lower my blood pressure. After a week I developed cramping and gas. I misdiagnosed myself as having diverticulitis as I believe the symptoms are similar. I wonder if anyone else experienced this problem.

By candyquilt — On Apr 01, 2012

I took l-arginine on and off for six months. I had a couple of l-arginine side effects that were worse in the beginning that slowly became less and less.

I don't have herpes but I'm prone to cold sores. I have always been and I get them a lot in winter. It was winter when I started taking l-arginine so I literally had 4 or 5 cold sores on my mouth back to back because of it.

I took several weeks off from l-arginine to let them heal and started with a lower dose next time. I think this is a good idea in general, to start off with a lower dose than what is recommended and slowly build up to the recommended dose. It's also a good idea to take a week off from it every couple of weeks so that it doesn't build up in the system.

The other side effects I had briefly were vivid dreams and nightmares when I took the supplement before going to bed. I also had an increase in erections in the beginning.

By ddljohn — On Mar 31, 2012

@turquoise-- I think I saw the same study but from what I remember of it, the results were still pretty theoretical. Researchers are not one hundred percent sure if l-arginine increased the risk of death for those heart attack patients who took it.

It is a well known fact that reduced blood pressure is a side effect of l-argenine though. So it doesn't counteract only with blood pressure medications but also any other medication which affects blood pressure as a side effect. Viagra for example reduces blood pressure so taking viagra and l-arginine together is a no-no.

By turquoise — On Mar 31, 2012

When I took l-arginine sometime back, I had to stop because I was getting really dizzy. I didn't have a blood pressure monitor at home so I don't know if my blood pressure fell, but it probably did. So I stopped taking it right away and I was no longer dizzy.

Later I read an article about l-arginine and studies that were done on it. They found that it could be dangerous for people with heart problems and a previous heart attack to take this supplement. Apparently it raises the risk of death from a heart attack.

So I think l-arginine needs to be taken only under doctor control and l-arginine dosage should probably be low. I don't have any heart or heart pressure related issues but it still affected me a lot. Who knows what it could do for someone who does have these problems.

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