PreSeries Stim-Free Pre-Workout Review


Transparent Labs refers to its PreSeries Stim-Free Pre-Workout as the “most exceptional… pre-workout supplement available.

The PreSeries Stim-Free Pre-Workout claims to:

  • Send nitric oxide to the muscles
  • Help you “gain lean muscle mass”
  • Enhance endurance and focus
  • Provide a high-intensity pre-workout experience

Sounds good so far. We haven’t tried a Caffeine-free pre-workout in a while, so this could be interesting. Here’s our PreSeries Stim-Free Pre-Workout review…

About the Company

Transparent Labs claims to stay true to its name by ignoring “pseudoscience” and “misleading research.”

Instead, it says it focuses on “key ingredients at clinically effective dosages”, “100% formula transparency” and “scientific studies.”

The company website decries the use of “deceitful marketing” and “low-quality products”, while going on to conclude that “our beloved supplement industry needs a change.”

No arguments here. But do the company’s supplements measure up?

The Ingredients and How They Work

The PreSeries Stim-Free Pre-Workouts uses a bunch of familiar ingredients. We’re glad to see some of them, disappointed to see a few and baffled to find others.

See for yourself:

PreSeries Stim-Free Pre-Workout ingredients

Citrulline Malate

It’s great to see a healthy 6000mg dose of Citrulline Malate at the top of this list of ingredients.

A potent blend of L-Citrulline (an amino acid) and Malic Acid (a Dicarboxylic Acid), Citrulline Malate should be one of your must-have pre-workout ingredients.

L-Citrulline derives from watermelons and boosts the level of nitric oxide in your blood. This in turn sends oxygen to your muscles to help them grow.

Meanwhile, Malic Acid helps reduce muscle soreness and fatigue by lowering the amount of ammonia in the blood.


BCAA (or Branched Chain Amino Acids) is an umbrella term for Valine, Leucine and Isoleucine. All three help the body synthesize protein and induce muscle growth.

However, most lifters and athletes get enough BCAA in their whey protein supplements, which anyone serious about working out should be taking.

As a result, the additional BCAA may be redundant here.

CarnoSyn Beta-Alanine

Beta-Alanine is a modified amino acid with a good rep as a pre-workout ingredient. A precursor to Carnosine, Beta-Alanine is said to reduce fatigue and help increase lean mass.

And while there is truth in these claims, we will never recommend Beta-Alanine. This is because it can cause itching, tingling, and prickling sensations. Some users liken these sensations to “pins and needles”, “burning” and the feeling of “sleeping limbs.”

This condition is known as paresthesia and many lifters report that it ruins their workouts.

Why using Beta-Alanine may be pointless here

Beta-Alanine does a similar job to Creatine. The key differences are that Creatine doesn’t cause the unpleasant “pins and needles” and boost testosterone to help muscle growth.

As this supp also contains Creatine, Beta-Alanine may just be taking up valuable space.

Creatine HCI

Creatine is naturally produced in the body. You’ll also find it in some foods, including meat, fish and eggs. But you probably won’t get enough of it in your diet to optimize your workout.

Taking Creatine in a supp helps lifters and athletes to increase strength, raise running capacity, reduce fatigue and enhance lean mass.

To this extent, it’s great to see Creatine in this supp. But while Creatine is a proven ingredient, the HCI (hydrochloride) form is untested compared to Creatine Monohydrate, which many – us included – believe to be the best of its kind.

BetaPure Betaine Anhydrous

Betaine naturally occurs in the body and you’ll also find it in beetroot, spinach, wine, cereals and seafood. While some research implies Betaine supplementation can improve exercise performance, other research casts doubt on this claim.

Besides, taking Betaine in supp form can lead to fishy body odor and breath.


The guys at Transparent Labs claim to include Taurine in this supp to help reduce muscle soreness.

Despite this, research shows the organic acid fails to reduce muscle damage or soreness to any real extent.

And while one study suggests a mix of BCAA and Taurine is effective for this purpose, we need to see the results of further research before we can recommend its use in a pre-workout.

N-Acetyl L-Tyrosine

N-Acetyl L-Tyrosine (NALT) is in this supp for its apparent ability to reduce stress during exercise.

And one study did show NALT can reduce stress due to exposure cold conditions or altitude. But there’s no proof it has the same effects on workout performance, either on military personnel or civilians.

Choline Bitartrate

Choline is largely found in eggs (esp. the yolk). It’s also known as a cognition booster, and for its ability to reduce fatty acids in the liver.

Many companies use the molecule in their pre-workouts to reduce fatigue, boost focus, speed up reaction times and raise training volume. But all of the available research shows Choline has no use for any of these purposes.

Mucuna Pruriens

Transparent Labs says it includes Mucuna Pruriens in this supp because it brings “both psychological and physical benefits to athletes.”

And one study suggests the herb can improve a user’s sense of well-being. But while this warrants further research, Mucuna Pruriens is wasted in a pre-workout.

This is because the reduction in cortisol that brings about this sense of well-being is minor compared with this herb’s T-boosting power.

So while Mucuna Pruriens is a worthy addition to any T-booster or libido enhancer, it’s puzzling that Transparent Labs uses the herb in all three of its pre-workouts.


The PreSeries Stim-Free Pre-Workout includes L-Norvaline to “up regulate” the nitric oxide synthase (NOS).

In basic terms, this means it’s supposed to work with Citrulline Malate to give you stronger pumps, power and energy.

But while early research shows L-Norvaline has promise for this purpose, there’s not enough proof (besides a ton of online hype) to defend throwing it in PreSeries Stim-Free Pre-Workout – or any pre-workout, for that matter.


BioPerine is a patented form of Black Pepper Extract (Piperine). Its main purpose is to help the body absorb more of the other nutrients in this supp.

PreSeries Stim-Free Pre-Workout pack

See SupplementTester’s Highest Rated
Highest-Rated Pre-Workouts Here

Side Effects

The ingredients in PreSeries Stim-Free Pre-Workout are safe to use.

However, Beta-Alanine may give you feelings of numbness, prickling or burning across your skin. Known as paresthesia, these symptoms are harmless, but many users find them distracting.

As part of a pre-workout’s job is to give you laser focus, you could find paresthesia ruins your workout.

Betaine and Choline also cause many lifters to experience fishy breath and body odor.

Pros and Cons


  • Citrulline Malate raises energy, reduces fatigue and curtails muscle soreness
  • Creatine helps increase strength, running capacity and muscle mass
  • No proprietary blends


  • Creatine HCI untested compared with Monohydrate version
  • Beta-Alanine may cause itching, prickling, or burning sensations across your skin
  • Betaine and Choline can make your breath and body secretions smell like rotten fish
  • Taurine does not reduce muscle damage or soreness
  •  No proof NALT affects workout performance
  • Research suggests Choline is useless as a performance enhancer
  • Mucuna Pruriens is better suited to a T-booster
  • Not enough research on efficacy of L-Norvaline

SupplementTester’s Highest Rated
Highest-Rated Pre-Workouts Here

PreSeries Stim-Free Pre-Workout Review Conclusion

PreSeries Stim-Free Pre-Workout contains one or two great ingredients – but that just isn’t enough.

Unlike a lot of supps, this pre-workout holds 6000mg of Citrulline Malate – which is pretty much the perfect dose for awesome pumps.

You’ll also find Creatine in this supp, which along with Citrulline Malate, should be one of your two must-have pre-workout ingredients.

Here’s what what you WON’T like

The use of the HCI form baffles us. Yes, Creatine is one of the most tested ingredients out there – but 99% of this research focuses on Creatine Monohydrate and not HCI.

As it stands, there’s no real reason (other than marketing hype) to use the newer form of Creatine.

The PreSeries Stim-Free Pre-Workout also contains three ingredients to put on your must-avoid list. Beta-Alanine causes unpleasant itching, while both Betaine and Choline could make your breath and body odor reek of rotten fish.

Meanwhile, there’s no proof NALT boosts workout performance and not enough evidence L-Norvaline can enhance muscle pumps.

Our verdict

Transparent Labs claims to base its formulas on science, but that doesn’t appear to be the case with PreSeries Stim-Free Pre-Workout. It contains too many ingredients that either don’t work or that might work.

With this in mind, ignore this pre-workout and search for one with better-studied ingredients at the ideal doses.

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