Phentaslim Review (UPDATED 2024) – Is It Safe?

614 Review(s)
AVG Rating: 3.8/10

Phentaslim is a product that boasts the unique benefit of annihilating body fat, at least according to the official website. What this product is, is it’s a metabolism booster that contains caffeine and amino acids.

The product is made by a company known as Optimum Nutra—a company known for selling a range of health supplements for weight loss, sexual function, and more. The makers of this product say that the formula is clinically proven, but right off the bat, we noticed that there were not any studies or scientific evidence provided that supported this claim.

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Phentaslim Overview

The makers of this product recommend taking the pills throughout the day to maximize the potential for weight loss. What this translates to is–users can take up to three pills a day.

Because this product has stimulant effects, users should avoid taking with coffee or other stimulants. Additionally, users are best off avoiding this product toward the later end of the day, as it may interfere with their ability to fall asleep.

Phentaslim is available exclusively through the Phentaslim website, One bottle costs $59.95, but users can save if they opt to purchase multiple bottles at a time.

As a point of reference, each bottle contains 90 capsules of Phentaslim, which should equate to a one-month supply, if taken as directed.

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Phentaslim Claims

Phentaslim claims to work through the use of a natural formula made up of 15 ingredients that aim to make weight loss easier and faster.

As per the website: the product helps improve mental clarity, mood, and eliminate cravings. It also helps burn calories and help you slim down. Added benefits include vitamins, minerals, and antioxidants present to help you keep your immune system in peak condition.

Here is a look at some of the key ingredients you can expect to find inside Phentaslim:

  • Guarana Seed
  • Caffeine Anhydrous
  • Green Tea
  • Raspberry Ketones
  • L-tyrosine
  • L-carnitine

Guarana Seed is an ingredient that contains caffeine, and as such, it’s used as a way to improve athletic performance, boost energy, mental performance, and more. This seed may also work as an appetite suppressant and is often used in energy drinks for its coffee-like effects.

Caffeine Anhydrous is a dehydrated form of caffeine used in supplements to stimulate the metabolism while simultaneously suppressing the appetite.

Green Tea is rich in antioxidants, which target free radicals in the body, protecting the body from environmental stressors that lead to aging, disease, and more. Some researchers believe that green tea might have a thermogenic effect, and help the body burn more calories after consuming.

Raspberry ketones are a diet ingredient popularized by Dr. Oz and are thought to help boost the metabolism and break down fat cells in the body. Some research in animals has shown that raspberry ketones might affect the metabolism, but the effects have not been sufficiently studied in human subjects.

The formula also relies on cayenne pepper, which contains the chemical, capsaicin. Capsaicin may boost metabolism with use. That said, a study from Purdue University revealed that while eating spicy foods can affect your metabolic rate, it doesn’t seem to work in people used to eating spicy foods. Like most of the ingredients included in the blend, caffeine, guarana, capsaicin works best on those who have a minimal tolerance built up.

Finally, amino acids L-carnitine, and L-tyrosine are present in the formula. The former is an amino acid that helps the body break down fats more efficiently, preventing them from being absorbed into the body’s fat stores, while the latter works to give the body energy and combat fatigue.

Interestingly, some users have claimed that this product is a carbon copy of the product, Phen 375. Both products do contain similar ingredients and boast a similarly troubling online presence.

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Word on the Street About Phentaslim

Most of the “word on the street” is put out there by the makers of Phentaslim. We were hard-pressed to find any results proving the link between this product and weight loss.

Phentaslim has a number of testimonials posted on their website, but it’s hard to separate out which entries were written to support the sale of this product and which were genuine reviews from happy customers.

Third-party sites don’t even sell this product, so there aren’t really any neutral forums that talk about this product and its use. Still, we found some comments about the Phentaslim experience.

The overall consensus from many users was that the high caffeine count in this product makes it hard to take long term, especially for those people who are sensitive to caffeine. Users build up a tolerance and eventually, you’ll need to take the product more often to feel the effects.

Though Amazon doesn’t sell Phentaslim, a few people took to the forum to share their thoughts. One person said that the supplement did help them lose weight, as it does a decent job suppressing the appetite. The user mentioned that they were dropping about a pound per week, nothing crazy, but it seemed like they were reasonably satisfied with the results.

The few reviewers we found stated that they probably wouldn’t repurchase this supplement, as progress was modest and at times this product caused some negative side effects.

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Is Phentaslim Worth a Try?

In the end, it’s worth pointing out that Phentaslim is an expensive caffeine pill. Users can expect to see a boost in energy, as they would if they simply drank too much coffee. If that’s what you’re after, you’re better off brewing a batch of black coffee and hitting the gym.

While caffeine is the most active component in Phentaslim, the manufacturer has attempted to make the product more enticing with the addition of vitamins and other nutrients.

Priced at around $60 for a one-month supply, Phentaslim is an expensive caffeine pill. Yes, all that caffeine will kick start your metabolism and encourage fat burning – but it’s not powerful enough to help you lose weight while you sit at home on the couch.

Sure, Phentaslim may provide you with some of that raw energy you’re looking for in a workout, but there’s no reason to choose this source of caffeine as opposed to coffee or even caffeine pills.  Phentaslim essentially packaged caffeine and charged users upwards of $60 a bottle. Users felt that it was hard to justify the costs.

It’s hard to say whether this product is worth trying. Most of the reviews we found said that the product was too expensive and not effective enough to warrant the $60+ investment.

We’re not sure if that judgement is based on the fact that the product didn’t work, or the fact that the product is mainly composed of caffeine—a cheap stimulant you can get by going to any supermarket or coffee shop.

For more about selecting a weight loss tool like a shake or a supplement–read through our collection of reviews for more information.

Phentaslim FAQ

  1. How do I take Phentaslim?
    According to the Phentaslim website, you’ll take one capsule 20 minutes before breakfast with water. You’ll make the second capsule 20 minutes before lunch, and one in the late afternoon with an early dinner or snack. Because of the caffeine content, you shouldn’t take this too close to bedtime; otherwise, you may have trouble falling asleep.
  2. Is Phentaslim safe?
    The makers of this product sidestep the question “are there any side effects associated with taking Phentaslim” by saying the FDA has approved all ingredients.
    Unfortunately, all kinds of ingredients are approved by the organization, but that doesn’t mean that the ingredients won’t interact with each other in a way that might be harmful to some users.
    Phentaslim is clearly a stimulant—as evidenced by the guarana, the caffeine, and
  3. Where can I buy Phentaslim and how much does it cost?
    Phentaslim is available for sale on the official site, The product is sold in various packages–a single bottle goes for $69 for a one-month supply (90 capsules), $109 for two bottles, and $159 for four bottles.
  4. Is there a money-back guarantee?
    According to, the product has a 60-day money-back guarantee–from the purchase date.

What Really Works?

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