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Transparent Labs BULK Pre-Workout Review: A Detailed Analysis of Its Safety and Effectiveness

Written by Markita Lewis, MS, RD

Reviewed by Anthony Dugarte, MD 

Last Updated on July 8, 2021

Dietitian Rating:


About This Rating
The average rating of this product is calculated based on the evaluation of the following factors:
  • Support for Claims:3.7
  • Ingredient Safety:3.0
  • Value for the Price:4.0
  • Brand Transparency:5.0

PreSeries BULK is a pre-workout supplement that is claimed to increase muscle mass and support testosterone. The research strength of some of the ingredients is lacking, but overall it appears to be a decent pre-workout supplement to add to your regimen.

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Transparent Labs BULK Pre-Workout Review: A Detailed Analysis of Its Safety and Effectiveness


  • Most ingredients are in clinically-tested doses
  • Priced well for formulation compared to competition
  • Clear information easily available concerning third-party testing


  • Some individual ingredients have small positive or mixed results in efficacy
  • Potential side effects from some ingredients

What Is BULK Pre-Workout?

PreSeries BULK is a pre-workout supplement designed by Transparent Labs for athletes and bodybuilders to increase their size and muscle mass.

Transparent Labs attempts to set itself apart from the competition by focusing on, you guessed it, transparency.

They promote transparency in their labeling and try to be transparent in their claims by only including ingredients linked to published research.

PreSeries BULK is available in 4 flavors – blue raspberry, sour grape, tropical punch, and strawberry lemonade.

Evaluation of Ingredients

The main ingredient profile for this supplement includes:

  • Citrulline Malate 2:1, 6,000 mg
  • Beta-Alanine, 4,000 mg
  • BCAA 2:1:1, 4,000 mg
  • BetaPure Betaine Anhydrous, 2,500 mg
  • Taurine, 1,300 mg
  • L-tyrosine, 1,000 mg
  • AlphaSize Alpha-GPC, 300 mg
  • L-theanine, 360 mg
  • Caffeine Anhydrous, 180 mg
  • Theobromine, 50 mg
  • DiCaffeine Malate, 30 mg
  • AstraGin, 25 mg

This supplement also contains a testosterone support complex made up of:

  • Vitamin D3, 75 mcg
  • Boron, 3 mg
  • Zinc, 30 mg

Testosterone has several functions in the body, including metabolism regulation, increasing muscle mass and strength, and decreasing fat mass.

Studies find a relationship between testosterone levels and muscle mass and strength, though the mechanism of action is currently unclear.

For this review, we will focus on the main BULK Pre-Workout ingredients and the testosterone support complex.

This supplement also contains vitamin B6 (pyridoxine HCl, 5 mg), vitamin B12 (methylcobalamin, 100 mcg), sodium (sodium chloride, 150 mg), and potassium (potassium chloride, 100 mg).

Citrulline Malate

L-citrulline is a non-essential amino acid made by the liver and the gut. It can be transformed into the amino acid arginine and nitric oxide.

Nitric oxide increases blood flow throughout the body, which helps decrease muscle fatigue and increases work capacity.

One small study found that supplementation of 8 g citrulline malate improved blood flow compared to a placebo. This could, in theory, improve exercise performance.

A different study with resistance-trained men found that supplementation of 8 g citrulline malate did not increase exercise performance and muscle gain response or change focus, energy, or fatigue.

A review of L-citrulline supplementation and exercise performance finds that the evidence supporting claims of enhanced exercise performance and recovery is inconsistent and more research needs to be done.

In these studies, no adverse effects were noted from taking this supplement ingredient.


Citrulline malate is an amino acid that can help blood flow through the production of nitric oxide but is not consistently shown to improve exercise performance and recovery.


Beta-alanine is a non-essential amino acid that combines with histidine to produce carnosine.

Carnosine is a protein-building block highly concentrated in the muscles, especially in athletes who do anaerobic exercise.

It is an antioxidant, helps maintain pH balance within the muscle, and may help with maintaining muscle force during exercise fatigue.

A meta-analysis of 40 double-blinded, placebo-controlled studies looking at the effects of beta-alanine on exercise performance found that supplementation of between 3.2 to 6.4 g/day can increase muscle carnosine and improve exercise capacity and performance.


Beta-alanine is an amino acid that has a role in producing carnosine, a protein-building block in muscles, and may improve exercise capacity and performance through antioxidant activity.

BCAA 2:1:1

This branched-chain amino acid ratio is for leucine (2000 mg): isoleucine (1000 mg): valine (1000 mg).

Leucine works with insulin to allow protein synthesis within muscles. The International Society of Sports Nutrition recommends that protein intake should contain 700–3000 mg of leucine with other essential amino acids to stimulate muscle growth.

Valine metabolism leads to the production of β-aminoisobutyric acid, which is secreted by muscles and acts on tissues to increase energy, improve insulin resistance and reduce inflammation.

Concentrations of the amino acids isoleucine and valine are decreased with leucine supplementation, so they are often included to reduce amino acid limits when synthesizing new muscle protein.


BCAAs (leucine, valine, and isoleucine) help protein synthesis within muscles and helps stimulates muscle growth.

BetaPure Betaine Anhydrous

Betaine is a derivative of the amino acid glycine, which can be used for creatine synthesis in the body.

Studies have found mixed results with the effectiveness of betaine for strength-based performance.

However, the effects of betaine supplementation (in doses of 2.5 g) seem to be more effective when strength training is accompanied by structured resistance training.

The research is limited on whether betaine supplementation improves body composition, but one study found that daily betaine supplementation (2.5 g/day for 6 weeks) increased lean mass and reduced fat.


Betaine anhydrous helps with creatine synthesis in the body but has limited research showing that it can help with improving body composition. It may also help with improving strength-based training, but research shows mixed results.


Taurine is an amino acid that is produced by the body. It is known to help reduce inflammation in certain tissues.

Research also finds that taurine concentrations are related to muscle performance and energy metabolism in muscle. Taurine may increase glucose intake within muscles and improve post-exercise muscle recovery.

A meta-analysis on taurine and endurance performance found that oral supplementation of 1–6 g of taurine slightly improved muscle performance.

In the studies included, no adverse effects were noted from taking taurine.


Taurine may slightly improve muscle performance during endurance exercise, improve post-exercise muscle recovery, and help glucose uptake in the muscles.


L-tyrosine is an amino acid that also serves as a precursor to the neurotransmitters dopamine and norepinephrine.

It is often used as a supplement for relieving stress and improving cognitive performance in short-term situations.

The research supports tyrosine as a supplement for cognitive performance, but it appears only to be effective if dopamine or norepinephrine are depleted.

The potential for tyrosine for improving exercise performance is limited as well, but more research needs to be completed.


L-tyrosine may help relieve stress and improve cognitive performance, but only if dopamine or norepinephrine are already depleted in the body from stressful situations. It also has limited efficacy in improving exercise performance.

AlphaSize Alpha-GPC

Alpha-GPC, or L-alpha glycerylphosphorylcholine, increases the release of the neurotransmitter acetylcholine and can support cognition, learning, and memory.

In one small study, college students took twice-daily doses of Alpha-GPC (approximately 600 mg/day) for 6 days.

After supplementation, students had an improvement in isometric mid-thigh pull strength, with a non-significant difference in upper body isometric strength.

No side effects were noted from taking the supplement in this study.


Alpha-GPC has limited research supporting it as a supplement for improving strength during physical activity.


L-theanine is an amino acid found primarily in green tea, which may decrease subjective stress and anxiety.

A 2019 review of studies found that L-theanine may help reduce stress and anxiety in individuals exposed to stressful conditions.

When combined with caffeine (75 mg), L-theanine (50 mg) can improve performance on attention tasks, improve mood, and eliminate the vasoconstrictive or behavioral effects of caffeine.


L-theanine may help reduce stress and anxiety, and when combined with caffeine, may improve attention and mood while reducing some negative effects of caffeine.

Caffeine Anhydrous

Caffeine anhydrous is a concentrated powder made from the dehydration of caffeine-containing plants.

Caffeine stimulates thermogenesis and increases the body’s calorie burn above normal to cause weight loss.

In addition to its ability to improve focus (as noted above), caffeine may improve sports performance.

A review of caffeine supplementation and performance in soccer players found that moderate doses of caffeine improved several soccer-specific abilities but did not decrease perceived exertion.

A small study of men doing high-intensity cycling found that caffeine consumption decreased subjective fatigue, reduced perception of effort, and improved time to exhaustion.


Caffeine anhydrous is a concentrated form of caffeine that can stimulate fat burning, improve focus, and may potentially improve sports performance.


Theobromine is a compound that is found in cocoa that binds to adenosine receptors in the brain.

Adenosine can regulate mood and behaviors, including anxiety and depression, but studies do not show a consistent relationship between theobromine and improved mood.

In one study, oral doses of theobromine at different concentrations (100 mg, 200 mg, and 400 mg) did not consistently affect mood or vigilance.


Theobromine does not have a consistent effect in improving mood.

Infinergy DiCaffeine Malate

Infinergy is a patented compound of two caffeine molecules with malic acid. This ingredient, created by Creative Compounds, is designed to prolong the effects of caffeine without any “caffeine crashes.”

Unfortunately, there were no studies available to compare the effectiveness of this Infinergy compound compared to regular forms of caffeine.


Infinergy DiCaffeine Malate is another form of caffeine that is formulated to reduce caffeine crashes.


AstraGin is an extract of the Astragalus membranaceus (Huang Qi) and Panax notoginseng (Korean red ginseng) roots, both of which are common in Chinese medicine.

Animal and cell studies by NuLivScience (the patent holder for this ingredient combination) find that adding AstraGin to proteins increases the absorption and bioavailability of amino acids in the gut.

This complex can also help activate the mTOR pathway (important in muscle building).

Some people who take astragalus may experience rash, itching, nausea, and diarrhea. In addition, panax notoginseng may cause dry mouth, flushed skin, nervousness, headache, nausea, and vomiting.


AstraGin was found in animal and cell studies to increase absorption and availability of amino acids in the gut and activate pathways needed for muscle building.

Vitamin D3 (Cholecalciferol)

Vitamin D helps regulate the synthesis of testosterone in the body, though the exact mechanism is still unclear.

Unfortunately, a recent review of studies on the effect of vitamin D on testosterone production does not show any significant clinical outcomes.


Vitamin D helps regulate testosterone synthesis, but supplementation does not show any significant increases in testosterone productions.

Zinc (Zinc AAC)

Zinc is a mineral important in the production of sex hormones such as testosterone.

In particular, an enzyme required to convert testosterone to dihydrotestosterone (a more powerful form of testosterone, responsible for male sex characteristics) is dependent on zinc.


Zinc is a mineral needed for testosterone production.

Boron (Boron Citrate)

Boron is an essential trace mineral. Research finds that boron can increase testosterone levels in the body, especially if previously on a low-boron diet.

One study found boron supplementation of 6 mg/day significantly increased free testosterone while decreasing inflammatory markers.

Boron also helps prevent vitamin D deficiency in the body by increasing the vitamin’s half-life.


Boron supplementation has limited research showing its ability to increase testosterone. It can help prevent vitamin D deficiency by slowing vitamin breakdown.

Verdict on Claimed Benefits

Below is our summary of the available evidence for the claimed benefits of BULK Pre-Workout based on the available research:

Gain size and muscle massStrong Evidence
Increase nitric oxide during workoutsStrong Evidence
Increase focus during workoutsStrong Evidence
Reduce fatigueModerate Evidence
Reduce muscle sorenessStrong Evidence
Enhance overall physical performanceStrong Evidence
Testosterone supportModerate Evidence

Side Effects, Safety, and Dosage

BULK Pre-Workout supplement should be taken approximately 20–30 minutes before exercising.

When first trying this supplement, Transparent Labs recommends starting with a 1/2 scoop of powder mixed with 8–15 oz of water to assess tolerance.

If able to tolerate without adverse symptoms, it is recommended to have 1 full scoop of powder mixed with 16–24 oz water.

PreSeries BULK Pre-Workout is free of artificial sweeteners, artificial coloring, artificial preservatives, gluten, and GMOs.

This product also contains a vegan source of BCAAs, making this product vegan-friendly.

BULK Pre-Workout contains two forms of concentrated caffeine. Taking this supplement along with other caffeine-containing beverages like coffee, tea or soda may put you at risk for having excessive caffeine intake.

The FDA warns against excessive amounts of caffeine and recommends limiting caffeine intake to no more than 400 mg daily (an equivalent to 3 or 4 cups of coffee).

Toxic effects of caffeine begin to appear with intake over 1000 mg, and higher doses have been associated with seizures and even death.

When using a supplement containing a stimulant, common side effects may include increased heart rate, insomnia, dizziness and lightheadedness, headache, diarrhea, feelings of anxiety or agitation, or upset stomach.

Betaine is associated with side effects including gastrointestinal upset, nausea, vomiting, diarrhea, bloating, and cramps, with rare cases causing cerebral edema.

Theobromine at large doses of 1,000 mg caused headache, nausea, and vomiting in some individuals during a clinical trial.

Additional possible side effects from astragalus and Panax notoginseng include rash, itching, nausea, diarrhea, dry mouth, flushed skin, nervousness, headache, and vomiting.

In a review, researchers sought to address potential safety concerns of multi-ingredient pre-workout supplements.

Generally, side effects were minimal, with no deleterious effects on blood chemistry, resting heart rate, or blood pressure.

Outside of the concerns for the ingredients included, concerns for supplement use include the potential for contaminants like banned ingredients, heavy metals, and potent stimulants.

Transparent Labs lives up to its name of transparency when it comes to the quality assurance of its products.

On their website, there are certificates of analysis for all of their products, for each product run, completed by a third party.

Third-party verified certificates of composition are also available for every product offered by Transparent Labs.

Before taking a new supplement like PreSeries BULK, please consult with your primary care provider or doctor to ensure that this supplement is safe for you.

BULK Pre-Workout Cost

A container of BULK Pre-Workout supplement costs $49 for 30 servings.

If purchasing multiple containers at once, discounts are available:

  • 2 containers for $89
  • 3 containers for $119

Transparent Labs offers one of the better return policies available.

You can receive a refund on dietary supplements within 90 days of purchase and if the contents of the supplement have not been entirely used.

Of note, this refund option is available only if purchased directly from the Transparent Labs website.

Comparison to Alternatives

After looking at some of the other available pre-workout supplements, PreSeries BULK Pre-Workout offers some things that the competition does not.

This supplement blend contains BCAAs and other amino acids, where some supplement brands, like the Beyond Raw pre-workout (popular at GNC retailers), offer fewer ingredients.

Thanks to Transparent Labs’ philosophy on transparency, PreSeries BULK also lists the amounts for all its ingredients instead of a proprietary blend that may or may not include clinically relevant concentrations of their ingredients.

The cost of BULK Pre-Workout is comparable to its competitors, but considering all of its ingredients, it is a good value for your money.

Other pre-workouts share a similar price tag but have fewer active ingredients.

The Bottom Line

If you’re the type of person to use a pre-workout supplement before you exercise, BULK Pre-Workout may be for you.

It contains a proper dosage and variety of amino acids to help muscle gain, doesn’t contain any unnecessary ingredients, and is easy to use.

This supplement does suffer from the fact that while most of the ingredients have clinical trials that may support their benefits, several ingredients have inconclusive results concerning how effective they can be.

Individuals who are sensitive to caffeine may have to be careful with this supplement due to two separate forms of caffeine being used in this pre-workout supplement.

If you’re thinking about adding this pre-workout, I recommend speaking with your doctor before starting a new supplement to ensure that it is safe for you.

If you have concerns about testosterone levels, a conversation with your doctor can also help you get the testing you need to get a clearer picture of your health.

A Word from Our RD

Pre-workouts may help you get through your session at the gym, but it’s not the only important thing for being able to endure during exercise.

Proper sports nutrition is dependent on the timing of meals, meal composition, hydration, and more.

Learning how to fuel your body to sustain you before, during, and after your workouts takes some planning. A registered dietitian (especially one specializing in sports nutrition!) can help you meet your goals.

If you’re looking for the best workout to meet your needs, look for a certified trainer who can help guide you to a safe workout routine that helps you achieve your fitness goals.

Try Transparent Lab BULK Pre-Workout

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