L-Citrulline: Everything You Need To Know

man getting his pump on with dumbbell curls

If you’re reading this article, you’ve probably heard of L-Citrulline.

You’ll can find it in a ton of pre workout and amino acid supplements these days, mostly aimed at enhancing exercise performance.

Most people think L-Citrulline is just a ‘nitric oxide booster’ that gives you better pumps in the gym, but extensive research has revealed it’s actually so much more.

I’ve read every just about every published study on L-Citrulline supplementation.  Although it’s not as well known as some other workout supplements, it’s without a doubt one of the most useful and effective.

By the end of this article you’ll understand why that is.

So, if you’re ready to become an expert on L-Citrulline, let’s get started…

What Is L-Citrulline?

L-Citrulline amino acid molecule

L-Citrulline is a non-proteinogenic, non-essential amino acid.

Non-proteinogenic just means it’s not used to construct proteins, and non-essential simply means the body is capable of making it itself.

Make no mistake though…

L-Citrulline is absolutely essential to our health.

Beyond that, supplementation with L-Citrulline–beyond what your body is capable of producing normally–has numerous proven benefits which we’ll go over shortly.

First, let’s quickly talk about what L-Citrulline actually is and what it does within the body.

Citrulline is a precursor to the amino acid, Arginine, which in turn is used to produce Nitric Oxide.

In other words, it’s absolutely essential for Nitric Oxide synthesis.

Nitric Oxide plays a vital role in regulating blood flow and cardiovascular function.  Without, it you’re screwed

This has earned L-Citrulline a reputation as a ‘NO Booster’, and it is, but that’s actually just one of it’s jobs.

Citrulline also plays a role in the Urea Cycle, a detoxification process by which Ammonia is converted into Urea and expelled from the body.

This is the often neglected role that is largely responsible for the beneficial impact of L-Citrulline supplements on exercise performance.

Both of these properties–being able to increase NO production and helping rid the body of Ammonia–are what make L-Citrulline such an effective performance enhancement supplements, but it has other benefits as well…

What Are The Proven Benefits Of L-Citrulline?

human body glowing

L-Citrulline isn’t nearly as well known as supplements like Creatine or BCAA supplements, but research has uncovered numerous benefits.

This has earned Citrulline a place as a key ingredient in pre-workout supplements, but the benefits extend outside of the gym as well.

At this point, L-Citrulline has been proven to do much more than just improve workout performance.  Still, that’s as good a place as any to start…

L-Citrulline Increases Muscular Endurance

Citrulline has been shown to increase muscular endurance.

More specifically, it increases the amount of reps you can do towards the end of your workout when muscular fatigue would ordinarily be setting in.

You see, the muscle fatigue you experience when working out is in part caused by Ammonia build-up in muscle tissue.

L-Citrulline, being a key player in the Urea Cycle, can reduce the amount of Ammonia that builds up in muscle tissue, thereby delaying muscular fatigue and allowing you to get more reps at a given weight.

Just to be clear…

Muscular endurance isn’t the same thing as strength.

  • Greater strength is being able to put up more weight.
  • Greater endurance is being able to put up a given weight more times.

So to say that Citrulline increases your strength would be false.  That doesn’t mean it can’t help you get stronger over time.

As long as you stick to the principle of progressive overload–continually increasing the amount of weight you lift over time–supplementing with L-Citrulline can help you get stronger.

The more reps you do at at given weight, the more weight you’ll be able to add to the bar over time.  The more weight you add to the bar over time, the stronger you get.

It’s pretty obvious that anyone who’s goal is to get stronger and build muscle over time stands to benefit from supplementing with L-Citrulline.

I mean, who doesn’t want to add a couple reps to their lifts?!

L-Citrulline Increases Nitric Oxide

Remember earlier?

We talked about how Citrulline is the direct precursor to the amino acid L-Arginine which is the immediate precursor to Nitric Oxide.

We also mentioned that Nitric Oxide supplements are one of the most sought after kinds of workout supplements for that very reason.

Well, that’s because anything that increases Nitric Oxide levels can potentially increase blood flow, resulting in some pretty nice pumps during workouts.

Unfortunately, most ‘nitric oxide supplements’ don’t really work.

Actually, L-Arginine is a perfect example

One would think that, since Arginine is actually closer to Nitric Oxide than Citrulline, supplementing with Arginine would be a better idea.

Makes sense, but that’s not the case at all.  In fact, it’s quite the opposite.

Studies which have looked at how Arginine impacts performance enhancement and blood flow have failed to find any real benefit.

This is because Arginine is subject to breakdown by the enzyme Arginase.

L-Citrulline, on the other hand, is not.  It bypasses Arginase, then converts into Arginine which converts into Nitric Oxide.

So, there’s really no doubt about it…

As a Nitric Oxide supplement, Citrulline is superior to Arginine.  If it’s better pumps and fuller muscles you’re after, you want L-Citrulline.

L-Citrulline Improves Cardiovascular Health

Given it’s role in Nitric Oxide production, it makes sense that Citrulline would be explored as a potential treatment for people with cardiovascular conditions.

And it has…

L-Citrulline has been shown to prevent hypertension in kids recovering from heart surgery but appears to encourage healthier heart function in healthy individuals as well.

Studies also show that it can prevent increases in blood pressure in people with high blood pressure, but does not lower blood pressure to an unhealthy degree in healthy people.

In other words…

Citrulline helps maintain healthy blood pressure but won’t drop it too low, as so many blood pressure medications (especially blood thinners) may do.

This makes it a natural and safe first-line defense against high blood pressure.

But of course, the pharma companies that make billions from sell medications for lowering blood pressure don’t want you to know anything about that, so I’ll just stop there…

Only your doctor can really make the call whether or not you need a supplement like L-Citrulline or some drug that thins your blood.

The point is this:

L-Citrulline plays a vital role in regulating blood pressure, so it make sense to at least consider supplementing with it if you’re concerned about your blood pressure.

L-Citrulline Helps With Erectile Dysfunction

Naturally, anything that helps maintain optimal blood pressure is going to attract the interest of Erecetile Dysfunction researchers, not to mention people suffering from ED.

After all, an estimated 40% of men experience ED at some point in their lives, so if there was a supplement that was safe, affordable, and potentially effective, A LOT of people would be interested.

Just look at Sildenafil (Viagra).  It’s one of the most widely prescribed drugs of all time!  Clearly there’s a market there…

If you’re like most people though, you’d rather try a safe, natural substance that’s found in watermelon before taking a synthetic drug that’s cooked up in a lab.

L-Citrulline supplementation has been shown to improve symptoms of ED, even at 1.5 grams daily.  The same dose of L-Arginine has actually failed to have any impact on ED whatsoever.

So yeah, if it’s better boners you’re after, L-Citrulline is worth a shot.

It’s no miracle cure for ED by any means, but you’ve got nothing to lose there and plenty to gain.

L-Citrulline Reduces Muscle Soreness

L-Citrulline has been studied in the area of performance enhancement enough to observe some pretty obvious benefits when it comes to recovery from exercise.

It’s actually been shown to reduce muscle soreness.

Although this was originally more of a positive side effects noted in one study, several other studies have now confirmed it.

L-Citrulline definitely reduces muscle soreness.

How exactly it works though, remains something of a mystery…

It my have something to do with L-Citrulline reducing free radical damage during workouts.

Free radicals are molecules which cause oxidative damage.  They’re suspected of contributing to muscle soreness, among other things.

Given Citrulline’s role as a free-radical scavenger throughout the body, it makes sense that it would indirectly reduce muscle soreness ordinary caused by free radicals.

Of course, this is pure speculation, but however it works, one thing is clear…

L-Citrulline is an effective supplement for reducing muscle soreness and enhancing exercise recovery in general.

L-Citrulline And Growth Hormone

Growth Hormone (GH) is involved in a ton of physiological processes including building muscle, burning fat, and supporting immune function.

When you exercise, you naturally secrete more Growth Hormone.

Combined with exericse, L-Citrulline supplementation has been shown to augment the increase in Growth Hormone.

It does not appear to be effective without exercise though, so it can’t actually be considered a GH-booster.

More of a GH-augmenter, if anything.

Also, it’s not clear whether the increase is large enough to really matter in the scheme of things.

Most supplements that “increase Growth Hormone” really only do it to a small degree and for a short period of time.  That’s probably the case with L-Citrulline supplementation.

It certainly won’t mimic the effects of taking actual GH or a GH secretagogue, like MK 677.

Still, it’s worth mentioning the relationship.

L-Citrulline May Be Synergistic With Leucine

Leucine is the most important amino acid when it comes to building muscle.

It directly stimulates mTOR, a signaling molecule which tells the body to start building proteins (muscle protein synthesis).

There is some preliminary evidence which suggests Citrulline may enhance Leucine’s signaling of mTOR.

This could potentially mean that L-Citrulline and L-Leucine are synergistic, but it’s an area that remains under-researched at this time.

We need a few more studies before drawing any solid conclusions about how Citrulline actually interacts with Leucine.

Theoretically though, it makes sense to include Citrulline anytime you’re supplementing with Leucine.

Especially when it comes to fasted cardio!

That’s why I included 6g of Citrulline Malate along with 4g of Leucine when I formulated Amino Beyond.


The Different Types Of L-Citrulline Supplements

man pouring L-Citrulline Malate into a shaker cup

You’ll typically find 2 types of L-Citrulline supplements:

  1. L-Citrulline
  2. L-Citrulline Malate

Throughout the research we discussed, we referred to both of these as L-Citrulline, but there is actually a difference between them which could potentially make one better than the other.

L-Citrulline is just free-form Citrulline.  

L-Citrulline Malate is L-Citrulline bonded with Malic Acid.

Malic Acid plays a major role in energy metabolism.  It may have it’s own inherent benefits, but no studies have really looked at Malic Acid supplementation alone in humans.

Only in mice.


The majority of the studies in which Citrulline enhance exercise performance and reduces soreness used L-Citrulline Malate.

That’s why Citrulline Malate tends to be used in pre-workout supplements, although plenty of them use L-Citrulline (because it’s cheaper).

L-Citrulline is still effective though if you dose it right.

Citrulline Malate is usually in a 2:1 ratio of Citrulline To Malic Acid.

That means 6 grams of Citrulline Malate would yield 4 grams of Citrulline and 2 grams of Malic Acid.

Needless to say, L-Citrulline and L-Citrulline Malate require different doses to be considered effective.

Citrulline Dosing

At this point, enough different doses of L-Citrulline and Citrulline Malate have been used across enough different studies to carve out a clinical dose (range) for each.

  • If you’re taking L-Citrulline, you want to take 4-5 grams.
  • If you’re using Citrulline Malate (2:1), shoot for 6-8 grams.

Unfortunately, due to the fact that Citrulline is expensive, most supplement companies under-dose it.

3 grams of Citrulline Malate won’t cut it!  At least not according the majority of the studies.

It’s possible that low doses of L-Citrulline are still effective, but we just can’t be certain.

Make sure you’re paying attention to your supplement facts panels and only buy clinically dosed supplements with no proprietary blends.

Does L-Citrulline Have Any Side Effects?

sign that says the words side effects

Not really…

At doses of 6-9 grams, absolutely no negative or adverse health effects have ever been reported.

This makes sense since L-Citrulline is simply an amino acid which your body is not only accustomed to, but requires to function properly.

If you were to take “too much” Citrulline, your body would just simply not absorb it.

The worst thing you could do to yourself with Citrulline supplementation is get a stomach ache if you ate like 20 grams in one sitting.

There’s really nothing to worry about with L-Citrulline at normal, effective doses.  It’s SUPER safe!

Obviously, this is the part where I say “check with your doctor before taking any supplement”, but the reality is:

Assuming you’re getting your supplements from a trustworthy brand–meaning they’re pure and uncontaminated–there’s nothing to worry about with L-Citrulline.

Should You Cycle L-Citrulline?

No, there’s absolutely no reason to cycle L-Citrulline, nor do you have to wait to see a noticeable difference in your ability to push more weight, recover faster, or get a better pump.

It’s quickly absorbed and works more or less immediately.

Some performance enhancement supplements like Creatine and Beta-Alanine require regular dosing for at least a couple weeks to see results, but that’s not the case with L-Citrulline.

The more regularly you use it either pre or intra-workout, the more strength gains will come, but you’ll notice a difference in your ability to get more reps at a given weight right away.

In this way, it’s similar to Alpha GPC.

My Opinion On L-Citrulline

I don’t go to the gym without it.

Usually I take Amino Beyond in a shaker and sip on it as I drive to the gym and during the warm-up part of my workout.

It’s fine to take it with your pre-workout supplement too.

Whatever gets it into your body so that it can be utilized during the intense parts of your workout (when you need it most).

As far as I’m concerned, L-Citrulline is a must-have supplement when it comes to working out.

You’re holding yourself back by NOT using it.

I’m not just basing that statement off the research though…

I’ve experimented with Citrulline ALOT and I can honestly say that it makes a noticeable difference when it comes to squeezing out those last couple reps, pumps, and recovery.

Again, there are several reasons to use Citrulline and zero reasons not to…

The Bottom Line On L-Citrulline Supplementation

bodybuilder getting ready to do barbell curls

If you want to get the most out of each and every workout, you want to supplement with L-Citrulline.

It’s been scientifically proven to:

  • Increase Muscular Endurance (More Reps, More Sets)
  • Reduce Muscle Soreness (Faster Recovery)
  • Increase Blood Flow (Better Pumps)
  • Benefit Cardiovascular Health
  • Treat ED

And it may even be synergistic with Leucine with regards to building muscle (more studies are needed in that area).

To top it all off…

It’s entirely safe!

Next time you reach for a pre workout or BCAA supplement, do yourself a faor and make sure it has a clinical dose of Citrulline (Malate) in it.

Have Anything To Add About L-Citrulline?  Comment Below…

Click to comment
To Top