C4 Ultimate Shred Review (2025): Is This Fat-Burning Pre-Workout Worth It?

We can all agree—your “gym juice” is only as good as what’s in it. But even the best pre-workout ingredients can’t take your training to the next level if you can’t choke them down. 

You know how we roll here at GGR. We’re all about honesty, even if it means shredding apart some products for the sake of factual reporting. In this C4 Ultimate Shred review, we’re revealing the good, the bad, and the taste that might burn your throat more than your workout.

Medical disclaimer: This article is intended for educational and informational purposes only. It is not intended as a substitute for medical advice. For health advice, contact a licensed healthcare provider. GGR also recommends choosing a product that has been third-party tested for quality.

We’ve Scooped, Sipped, and Survived 100+ Pre-Workouts

GGR’s expert testers—including certified personal trainers, registered dietitians, nutrition coaches, and strength specialists—have gotten hands-on with more than 100 pre-workout supplements to date. From the best stim-free pre-workouts to those whose energy stores can (figuratively) set your hair on fire, we’ve reviewed and felt them all.

Every pre-workout goes through our in-depth pre-workout testing methodology, which scores products across key categories like:

• Price per serving: Pre-workouts under $1 per serving tend to score higher, while pricier options over $2 generally score lower, though profiles may earn value points with the presence of standout features like evidence-based formulas or third-party testing.
• Ingredients and formulation: Top scores go to transparently labeled products with clinically backed ingredients—think caffeine and l-citrulline—in research-supported doses. Products should also be free from unnecessary fillers and potentially harmful stimulants like synephrine and DMAE. 
• Available flavors: Taste is subjective, so we combine tester feedback and customer reviews to gauge flavor, aftertaste, and variety. Bonus points are awarded to brands offering multiple flavors—if one’s a miss, another might score a tastebud touchdown. 
• Solubility: A quality pre-workout should mix smoothly with little to no grit, clumps, or “floaties.” We test how well each powder blends right after shaking and note any hints of particle separation after the beverage has sat for a few minutes.
• Pre-workout effects: We track how each product performs in the gym—energy, pumps, and focus included—while noting any potential downsides such as jitters or digestive issues.
• Third-party testing: Since the FDA doesn’t regulate dietary supplements, third-party testing helps ensure label accuracy, purity, and safety. We look for certifications from trusted organizations—like NSF Certified for Sport, Informed Choice, and BSCG—and value brands that disclose their testing results.

C4 Ultimate Shred

GGR Score

We test and review fitness products based on an independent, multi-point methodology.

3.4

C4 Ultimate Shred

High caffeine

Multiple flavors

Not third-party tested

Free shipping for orders over $55

Not third-party tested

Subscribe and save 20%

Check Price

Product Type

Pre-workout powder with 300 mg of caffeine per serving

Price Per Serving

$2.75, or less if you subscribe

Flavors

Frozen Bombsicle, Cherry Limeade, Orange Creamsicle, Pink Lemonade

Third-Party Testing

None

Intense Workouts

With a blend of energy-boosting ingredients, you should have ample energy to crush your gym sessions.

Focused Lifters

Brain-boosting Tyrosine, Hyperzine A, and caffeine can help enhance your mental focus during your workouts.

Pros of C4 Ultimate Shred

Contains ingredients linked with increased metabolism

Good taste

300 milligrams of caffeine

Subscribe and save option

Cons of C4 Ultimate Shred

Some key ingredients, like L-Citrulline, are underdosed

Expensive if not placed on a subscription

Price per serving

$2.75

Flavors

Frozen Bombsicle, Cherry Limeade, Orange Creamsicle, Pink Lemonade

Total Servings

20

Key ingredients

Caffeine, tyrosine, dynamine, beta-alanine, l-citrulline

C4 Ultimate Shred contains numerous ingredients proven to increase your metabolism, which could lead to weight loss. Although some key ingredients, like l-citrulline, are underdosed you will get a big energy boost from the 300 milligrams of caffeine and other stimulants in this pre-workout.

A Quick Look at Cellucor C4 Ultimate Shred 

Cellucor is a sports nutrition brand helping you, as the brand puts it, “Evolve into your 2.0,” through a lineup that includes protein powders, amino acids and BCAAs, fat burners, creatine, and testosterone boosters. The brand’s flagship C4 lineup spans across zero-sugar energy drinks and a range of pre-workout powders, including C4 Original, C4 Ripped, and C4 Ultimate.

C4 Ultimate Shred builds on the high-stim C4 Ultimate formula as a fat-burning pre-workout, featuring ingredients to help support metabolism and weight loss. As with any supplement, though, there are a few things to know before you finalize your online cart.

Before You Buy

• Cellucor warns that C4 Ultimate Shred should not be used by anyone taking certain medications—such as nitrates or antidepressants—or by those with heart conditions or other medical concerns, as its ingredients may interact with or worsen these issues.
• You’re likely to find more flavor variety via Cellucor’s Amazon storefront, but buyer beware: Our tester calls this one of the “worst-tasting” supplements they’ve ever tried, and customer reviews reflect similar sentiments.

Is C4 Ultimate Shred Worth It?

At $2.75 per serving, C4 Ultimate Shred is pricey compared to some of the best pre-workouts, which typically cost $1.50 or less. That said, it could be worth the splurge for the right user.

Great for:

• Those seeking a pre-workout formulation with potential weight management perks 
• Experienced gym-goers or advanced lifters who want a high-stimulant pre-workout
• People who prioritize energy and endurance over flavor—we’ve consistently seen negative taste reviews online

Not recommended for:

• Beginners new to pre-workout powders or those sensitive to stimulants 
• Anyone looking to avoid caffeine, beta-alanine, or artificial ingredients 
• Competitive athletes who need third-party tested supplements

C4 Ultimate Shred Specs

Experience Using C4 Ultimate Shred

Matt Dustin, CSCS, PN1-NC, gave Cellucor C4 Ultimate Shred pre-workout a thorough trial run. The main takeaway? A bit of a love-hate experience.

Matt shares,“I don’t want to hate on this too much since C4 is known for great flavors, and most are, in fact, tasty. However, all the spicy ‘metabolism boosters’ they added ruin the whole thing, in my opinion. I’m actually shocked by how bad this tastes.” The silver lining? Matt had a solid workout, and it has an average rating of 4.4 out of 5 from online customers. 

All to say, there’s plenty to unpack, so let’s dive into Matt’s experience and see how C4 Ultimate Shred stacks up.

Price Per Serving

C4 Ultimate Shred costs $54.99 for 20 servings, which equates to about $2.75 per scoop. We typically like to see pre-workout prices closer to $1.50 per serving (or less), so this price tag earns Ultimate Shred a 2 out of 5 in this category.

Formulation

C4 Ultimate Shred combines over 10 active and patented ingredients across three “complexes” to support energy, endurance, and thermogenesis. It also contains B vitamins and electrolytes like sodium, potassium, and calcium for energy metabolism and hydration.

If the long label feels overwhelming—and rightfully so—here is a more digestible breakdown:

• Endurance & Performance Complex: Includes 3.2 grams of CarnoSyn beta-alanine¹ for muscular endurance, plus 3 grams each of l-citrulline² and l-arginine to boost nitric oxide production, blood flow, and muscle pumps—though citrulline sits below the optimal 6- to 8-gram range. BetaPower betaine anhydrous³ may aid power and strength, but is underdosed, as well, at 1.25 grams, while the 200 milligrams of PeptiPump is a newer ingredient with limited research.
• Ultimate Energy, Focus & Stimulant Matrix: Packs 300 milligrams of caffeine anhydrous for a strong energy boost, supported by 1 gram of l-tyrosine for focus—though it’s on the low end and typically more effective when paired with theanine⁴ (which this formula lacks). Dynamine (methlylliberine) and TeaCrine (as theacrine) may help sustain alertness in gamers⁵, but both are underdosed here and show limited evidence for enhancing exercise performance⁶. Huperzine A⁷ and Rauwolfia vomitoria root bark extract may further support focus, though research on both is mixed and limited.
• Enhanced Fat-Burning Matrix: Combines MitoBurn (beta-aminoisobutyric acid⁸), Oligonol⁹ lychee and green tea extracts, CaloriBurn grains of paradise¹⁰, and cayenne extract to support metabolic health and fat loss through thermogenesis¹¹—the process of producing heat and burning more calories. However, most research on these ingredients is limited.

C4 Ultimate Shred features several well-researched ergogenic ingredients, with Matt acknowledging that most are properly dosed and labeled clearly. Plus, we do appreciate the higher caffeine counts per serving, which can be excellent for major energy boosts pre-training. However, the inclusion of lesser-studied compounds, artificial ingredients, and the fact that some compounds may negatively interact with certain medications keeps its formulation rating at 3.5 out of 5.

Taste and Solubility 

Matt rated the taste a 1.5 out of 5 and didn’t hold back, noting, “Okay, the taste is AWFUL and Amazon reviewers seem to agree. At first, the Strawberry Watermelon is pleasant and sweet, but the aftertaste is actually spicy. It burns on the way down and leaves a horrible aftertaste.”

He’s not alone, either, and one reviewer took it even further. “The flavor is so horrible. It fuels my nightmares more than my workouts,” they state. “If I had to choose between continuing to use the Orange Creamsicle flavor and spending 30 minutes in a durian-scented steam room every day, I’d choose the steam room 11 times out of 10.” For perspective, durian is a fruit so pungent that it’s banned in some public places around the world … Woof. 

Fortunately, C4 Ultimate Shred’s mixability fared better with a 4.5-out-of-5 rating. Matt said it blended “pretty good” with a blender ball. “I saw some minor separation in my shaker bottle, but hardly any clumps,” he adds.

Side Effects

“For most adults, pre-workout supplements are generally safe for consumption,” notes Dr. Raj Dasgupta, MD, “But they can have some potential side effects.” When it comes to C4 Ultimate Shred, Matt rated this pre-workout powder at 3.5 out of 5 for side effects, saying, “I had a lot of energy and a great pump,” though he noticed the familiar, yet harmless tingles from the present beta-alanine.

Post-workout, however, was less favorable. “Very strong effects with an equally strong crash,” he shared, crashing hard once it wore off. He also experienced a bad headache and mid-day exhaustion, wondering if a half serving would’ve led to a better overall outcome. 

If you’re particularly sensitive to heightened caffeine counts or feel unsure of your body’s tolerances to specific ingredients, Dr. Raj suggests, “Start with a lower dose and talk to your doctor before taking a pre-workout [such as C4 Ultimate Shred], especially if you have any underlying health conditions.”

RELATED: Best Natural Pre-Workout

Third-Party Testing 

Matt notes that the C4 Ultimate Shred label “seems very transparent,” and he was impressed that each ingredient and dose was clearly listed. However, despite Cellucor offering other supplements that are NSF Certified for Sport, neither he nor I could find third-party certifications for C4 Ultimate Shred, resulting in a 3-out-of-5 rating in this category. 

C4 Ultimate Shred vs Transparent Labs BULK

Transparent Labs BULK

GGR Score

We test and review fitness products based on an independent, multi-point methodology.

4.8

Transparent Labs BULK Pre-Workout

Naturally sweetened

Multiple flavors

Third-party tested

No sugar added

45-day guarantee

Subscribe and save

Check Price

Read Full Review

Product Type

Pre-workout formulated to help support muscle gain

Price Per Serving

$1.67, or less if you subscribe

Flavors

Blue Raspberry, Strawberry Lemonade, Peach Mango, Tropical Punch, Watermelon, Strawberry Kiwi, Sour Grape, Black Cherry, Pineapple Coconut

Third-Party Testing

Informed Choice

Athletes

Third-party testing means it’s safe for those who may be subject to drug testing

Serious Lifters

With research-backed doses of citrulline malate and beta-alanine to enhance muscular strength and endurance, you’re sure to get the most out of each workout

Natural Shoppers

This formula contains no artificial sweeteners, fillers, or dyes

Pros

Third-party tested

Transparent ingredient list

Multiple flavors available

45-day money-back guarantee

No artificial sweetener or coloring

Cons

No creatine

Some users report that it tastes bad

Price per serving

$1.67

Flavors

Blue Raspberry, Strawberry Lemonade, Peach Mango, Tropical Punch, Watermelon, Strawberry Kiwi, Sour Grape, Black Cherry, Pineapple Coconut

Total Servings

30

Key ingredients

Citrulline-malate, beta-alanine, caffeine

Transparent Labs’ BULK supplement is attractive to those whose primary focus is split between potential muscle gain and a pre-workout pump. While the taste is questionable, the product works well for most users.

What our tester says:

“The Blue Raspberry flavor is exactly what you’d expect from your typical Blue Razz—it’s not too sweet either, which I like.”

C4 Ultimate Shred and Transparent Labs BULK are both caffeinated pre-workouts with ergogenic ingredients, though there are distinct differences between the two: 

• Caffeine content: C4 Ultimate Shred delivers 300 milligrams of caffeine per serving, compared to 200 milligrams in Transparent Labs BULK.
• Formulation: Both include research-backed ingredients like beta-alanine and l-tyrosine, but C4 adds several fat-burning compounds; some of which lack strong clinical support. Transparent Labs, on the other hand, features additional ingredients such as taurine, citrulline malate, l-theanine, and alpha-GPC in clinically effective doses.
• Ingredient quality: C4 Ultimate Shred contains artificial flavors and sweeteners, while Transparent Labs BULK uses natural ingredients. 
• Third-party testing: C4 Ultimate Shred is not third-party certified, whereas Transparent Labs BULK is Informed Choice tested with a Certificate of Analysis (CoA) available online showing testing results for heavy metals, banned substances, and purity.
• Cost: C4 Ultimate Shred costs about $2.75 per serving, while Transparent Labs BULK is more affordable at roughly $1.66 per serving.

Still deciding? Check out our full Transparent Labs BULK review and comparison table below for more details.

Customer Experience 

Cellucor earns a 5 out of 5 for customer experience, largely thanks to its generous 90-day money-back guarantee, which Matt calls “very impressive for supplements.” He adds, “From what I can tell, you don’t even have to return the product,” though Cellucor may request it back for quality issues.

The support team is easy to reach via phone, chat, or email. While Amazon’s return policies can be stricter, Matt points out that, “Cellucor says you can reach out to them directly as long as you bought it from an authorized retailer and have your receipt.”

RELATED: Strongest Pre-Workout

Ordering C4 Ultimate Shred

You can order C4 Ultimate Shred directly from Cellucor’s website by choosing your flavor, order quantity, and either a one-time purchase or subscription.

It’s also available on Amazon with more available flavor options, though you’ll miss out on Cellucor’s subscription savings and free shipping—unless you’re an Amazon Prime member.

Customer Reviews

C4 Ultimate Shred has a 4.4-star rating across Amazon and the Cellucor website, based on over 1,200 reviews. Matt sums it up by noting, “Most agree with me—amazing effects, but one of the worst-tasting products of all time.” Orange Dreamsicle appears to be the most off-putting flavor, but many appreciate the formulation’s energy boost for workouts. 

Final Verdict of Our C4 Ultimate Shred Review

C4 Ultimate Shred is a high-stimulant pre-workout designed to deliver strong energy, endurance, and fat-burning support. Before you scoop, here are a few key takeaways:

• Packs 300 milligrams of caffeine—great for experienced users, but likely too intense for beginners.
• Includes several ingredients for endurance, focus, and fat-burning, though some are underdosed and less studied.
• Our tester called it “one of the worst-tasting supplements” he’s tried, with many customers echoing similar thoughts. 
• At $2.75 per serving, it’s on the higher end, but it may be worth it for those seeking intense energy and thermogenic effects.
• Transparent labeling, but lacks third-party certifications like NSF Certified for Sport.

Cellucor C4 Ultimate Shred

C4 Ultimate Shred contains numerous ingredients proven to increase your metabolism, which could lead to weight loss. Although some key ingredients, like l-citrulline, are underdosed you will get a big energy boost from the 300 milligrams of caffeine and other stimulants in this pre-workout.

Product Brand: Cellucor

Product Currency: USD

Product Price: 54.99

Product In-Stock: InStock

Editor's Rating:
3.4

C4 Ultimate Shred Review: FAQs

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any diseases.

References

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