Your heart health is important. One way to keep your heart healthy is by maintaining normal blood pressure. (Normal blood pressure reads less than 120/80.) Blood pressure is the force of your blood against your artery walls. When your blood vessels are narrow and constricted, this increases your blood pressure. High blood pressure, or hypertension, has few outward symptoms and can lead to heart disease, heart attack, stroke, or heart failure. Naturally, one way to lower high blood pressure is to relax and open up your arteries. Two natural substances that do this are l-arginine and l-citrulline.

What is L-arginine?

L-arginine is a non-essential amino acid. Non-essential does not mean that it isn’t important: it just means that you do not depend only on your diet to get it. Your body can produce it, but it is also found in foods like spinach, lentils, soybeans, turkey, seafood, peanuts, and pumpkin seeds. Or it can be taken as a supplement.

When your body receives or makes l-arginine and it enters the blood vessels, it stimulates cells in the inner layer of your blood vessel wall. These cells produce an enzyme called Nitric Oxide Synthase (NOS). Along with other cofactors, NOS is able to take the l-arginine and convert it into nitric oxide. Fun fact: During this process, l-citrulline is produced.

What is L-citrulline?

Watermelon slices on vibrant concrete slate

L-citrulline is similar to l-arginine. It is also a non-essential amino acid; your body can produce l-citrulline on its own. And as we just learned, l-citrulline is also a by-product of l-arginine being converted into nitric oxide. But you can still get it from foods such as watermelon, legumes, meat, and nuts. Most people use supplements to increase their intake of l-citrulline.

Like l-arginine, l-citrulline is converted into nitric oxide by the NOS enzyme. It can also be converted into l-arginine. Both are very useful, and they can be doubly powerful when they are taken together.

What Does Nitric Oxide Do?

Red and white blood cells in the vein. Leukocyte normal level

So, you have taken a supplement of l-arginine or l-citrulline (or both) and your body now has nitric oxide. Now what? Nitric oxide is helpful because it helps your blood vessels dilate. Nitric oxide moves into middle layer of the blood vessel wall (called the vascular smooth muscle) and makes the smooth muscle relax. Your blood vessel widens and your blood can flow easily. With that, your blood pressure lowers and you are able to maintain a healthy heart.

Besides lowered blood pressure, there are many other benefits of nitric oxide and its effects on blood vessels. Athletes often take nitric oxide supplements to improve their performance because it improves blood flow. One case study shows the effects of an oral combination of l-arginine and l-citrulline in male athletes. After seven days, results showed improved performance in a 10-minute cycling test and physical exertion. However, other studies and research doubt whether l-arginine and l-citrulline actually improve endurance, but most agree that these supplements can help increase exercise tolerance and improve exercise performance in patients with heart disease.

Nitric oxide

Nitric oxide can also help those with mild to moderate erectile dysfunction. WebMD states, Taking 5 grams of L-arginine by mouth daily seems to improve sexual function in men with ED.” There is not enough evidence as to whether l-citrulline has the same effect. (But don’t forget l-citrulline can be converted to l-arginine in the body.)

Some animal studies suggest that NO might also help effects of diabetes, including blood vessel problems and wound healing. More studies (especially human trials) are needed to confirm this theory.

These are the most known benefits of l-arginine and l-citrulline; other benefits are constantly explored by medical researchers. But the main benefit of lowered blood pressure and improved blood flow always stands out and remains constant. Consider what l-arginine and l-citrulline can do for you.

Side effects and Interactions


Side effects

  • Can cause abdominal pain, bloating, diarrhea, gout, and blood abnormalities
  • Can make allergy symptoms and asthma worse
  • Lowers blood pressure (not always safe for people with low blood pressure)


  • L-arginine is possibly safe to use short-term during pregnancy or breastfeeding
  • It is possibly safe for infants and children when given appropriate doses
  • Should be used with caution for people with cirrhosis
  • Evidence suggests l-arginine makes herpes worse
  • May increase the risk of death after a heart attack
  • Causes dangerously high potassium levels in people with kidney disease
  • Do not take 2 weeks before a scheduled surgery
  • Should not be taken be those with Guanidinoacetate methyltransferase deficiency (those with this inherited condition cannot convert arginine to creatine)


  • Medications for high blood pressure. Taking l-arginine with blood pressure medication may cause the blood pressure to become too low.
  • Medications that increase blood flow to the heart (nitrates). Taking l-arginine with these can cause dizziness and lightheadedness.
  • Sildenafil (Viagra). Like medications for blood pressure, taking l-arginine with sildenafil (Viagra) can cause blood pressure to be too low.


Side Effects

  • Lowers blood pressure


  • There is not enough evidence to know whether l-citrulline is safe while pregnant or breastfeeding


There is little evidence on l-citrulline and potential interactions. Because l-citrulline also lowers blood pressure, refer to l-arginine interactions. Always talk with your doctor about taking an l-citrulline supplement to lower your blood pressure, especially if you are already taking blood pressure medication.

The Bottom Line

L-arginine and l-citrulline are both amino acids that are converted into nitric oxide in the body. Nitric oxide relaxes and opens the blood vessels, lowering blood pressure and providing other benefits. These supplements can improve athletic performance, help those with erectile dysfunction, and heal symptoms of diabetes in the blood vessels.

Talk with your doctor to see if l-arginine and l-citrulline are right for you. Your heart and health can improve, so why wait? Our L-arginine Plus supplement contains 5,110 mg of l-arginine and 1,010 mg of l-citrulline. Try it today!


Shop Now

Get 10% Off Instantly Today

Get 10% off your purchase on ElementsofHealthCare.com instantly! 

You have Successfully Subscribed!