Updated: 04/18/2017 - Site operated by Leptigen
By Summer Banks Apr 04, 2017

Looking at some diet products, like Phentaslim can be painful, especially if there’s no scientific backing for the formula. Let’s find out if this time is the same thing. We did some intensive research and created one of our in-depth reviews, examining the side effects, ingredients, clinical studies and overall customer experience. Also, we scoured hundreds of dieter comments found online. At this point, we compressed all the data to give you the info you need.

Phentaslim Readers: Click here to find out why we're giving away samples of our product, Leptigen.

What is Phentaslim?

To start, Phentaslim is a metabolism booster. The ingredients are guarana seed, [1] caffeine anhydrous, green tea extract, magnesium, zinc acetate, cayenne pepper, [2] panax ginseng root, L-tyrosine, L-theanine and L-carnitine. Supposedly it helps by boosts energy levels, decreases hunger and reduces excess body fat. This should be taken 20 minutes prior to breakfast, lunch and dinner along with a glass of water.

Phentaslim is made by Optimum Nutra Inc. and has been available since 2012. It can be purchased via the official website for $59.99. This supplement is backed by a 30-day satisfaction guarantee and there are some user testimonials posted on the site, but read on…

Fad Ingredients – “No Proof?”

The first thing we felt needed attention with Phentaslim ingredients was the fact that some are nothing more than a fad. “This one relies on an unproven formula that contains cayenne pepper and panax ginseng root; [3] neither of which has been proven to assist with weight-loss,” said our Research Editor.

One customer stated, “Not effective at all. Been taking for six weeks now.”

“Another scam pill. Doesn’t work like it’s supposed to.”

Negative Phentaslim Reviews – “That’s Not Good”

It’s always a good idea to check out Phentaslim reviews posted online. One person stated, “I started Phentaslim on 6th Dec. Not seen any weight-loss yet. But I feel more energy. [4] But since couple of days I am feeling dizziness and heavy head after consuming the medicine. The headache is quite a lot.”

Another said, “Serious jitters and nausea from this diet pill.”

After doing some extensive research, we came to the conclusion that if there is an individual aspect of a fat loss pill or diet system that is quite troublesome (too many negative reviews, fad ingredients, serious side effects) the real likelihood of lasting weight-loss results is minimal. This means if Phentaslim reviews and discouraging claims are true, this could be a serious dilemma.

The Science – “Clinical Backing?”

Even though the official website states that Phentaslim ingredients are supported by clinical research, we could not find the actual studies presented by the company. This is a shame, because there are a few bright lights in there. [5] Here at DietSpotlight, we need to see documentation of real science before we can get behind a weight-loss product.

Also: read our Leptigen Weight-Loss Kit review »

The Bottom Line – Does Phentaslim Work?

Well now, has the time come to rush out for this one? While there is definitely a lot of hype in a few Phentaslim reviews, we wanted to know if it works. We like that there’s research backing some of the ingredients and that we found a few positive comments. It’s a bit concerning that a few comments mentioned side effects.

If you want to lose those extra pounds, we suggest a supplement that doesn’t rely on fad ingredients and supported by positive reviews.

Among the best products we’ve seen this year is our product called Leptigen. With this one, you have four ingredients. All clinically-tested with results commonly found in journals such as Obesity and the Journal of Medicine.

Also, we’re so confident that you’ll love our supplement that we’re offering a Special Trial Offer, which is a good sign.

Previous Phentaslim Review (Updated June 17, 2014):

Phentaslim - What You Should Know

Phentaslim is a fat burning, weight loss supplement that looks pretty fantastic at first glance. A complete list of ingredients, with amounts for each, contact phone number and clinical support for ingredients are all listed on the official website, but when we looked deeper into the company there are a few red flags customers need to know about.

List of Ingredients


  • Thiamin
  • Riboflavin
  • Vitamin B6
  • Vitamin B12
  • Zinc
  • Niacin
  • Guarana Seed
  • Caffeine Anhydrous
  • Green Tea Extract
  • Cayenne
  • Raspberry Ketones
  • L-Tyrosine
  • L-Carnitine
  • 5-HTP
  • Panax Ginseng Root

Product Features of Phentaslim

The first six ingredients in the formula are nothing more than everyday vitamins. Pull out that bottle of vitamins you take every morning and you’ll likely find every one of these ingredient in higher doses, most of the time. Taking more of these vitamins and minerals is not going to improve overall health or weight loss. B vitamins are often marketed to increase energy, but the short half-life and the body’s inability to store the vitamins means a barely noticeable bump in energy before the body pushes those B vitamins out during urination. Most of the time with supplements intended to lose weight, don't always work. One thermogenic that has other great ingredients like Phentalsim, is Hydroxycut, which can be taken once or twice daily for the best weight loss results.

Moving on to the active ingredients, we notice nothing spectacular. Guarana, green tea and caffeine are all proven to boost energy and metabolism. And if it's caffeine and energy you seek, you may want to take a close look at Cellucor Super HD or Lipodrene, that carry various ingredients for energy, fat burn and appetite suppressants. What dieters are looking for is this huge bump in energy and mood so they feel like eating right and exercising. That is not exactly what Phentaslim will provide. We like the fact that Phentaslim adds only 100 mg of caffeine, but guarana and green tea are both sources of caffeine, so there is more than 100 mg per serving. We have no idea how much caffeine these ingredients add, but if both are standardized to just 50 mg of caffeine the dose jumps to 200 mg per serving. We found no appetite suppressant in Phentaslim, another huge problem. Caffeine increases metabolism and thus increases hunger.

A hidden problem with Phentaslim is revealed in the terms and conditions. If order Phentaslim and you just don’t like the product, you can return it for a refund, but you will pay $10 for the return, you will not receive a refund for and original or return shipping costs and the company retains your personal contact information to sell or share with other companies. If this seems to risky, perhaps an alternate choice for weight-loss is offered with Ideal Shape. They uphold to their money-back guarantee.


  • All ingredients are listed online.
  • Not too much caffeine is included per dose.


  • There are multiple stimulants in the formula.
  • The company charges a return fee.
  • Your personal information will likely be shared with other companies.

Phentaslim - Conclusion

Most of the ingredients in Phentaslim are well-known, clinically tested and safe for use by healthy dieters, but the gauge of a good company is about more than just the ingredient list. Behind the scenes we find a company that sells or shares your personal information and charges you to return the product if it doesn’t work for you. You can find a more effective supplement from a trustworthy company. One as such is BellyTrim XP which contains conjugated linoleic acid (CLA) a known ingredient that aides in weight loss.

Phentaslim Questions & Answers:

We boiled down hundreds of user comments about Phentaslim into this helpful FAQ.

What are the side effects of Phentaslim?

Phentaslim side effects may include jitters, nausea, dizziness, and headache.

What are the ingredients in Phentaslim?

Phentaslim ingredients are green tea [1], caffeine, l-theanine, l-carnitine, l-tyrosine, panax ginseng, guarana seed, magnesium, cayenne pepper, niacin, zinc, black pepper extract, vitamin B6, riboflavin, thiamin, and vitamin B12.

Does Phentaslim work?

The Phentaslim formula is not bad. It contains green tea and caffeine, two important ingredients. [2] However, you can find these in hundreds (if not thousands) of other products. Some parts of the supplement have no clinical support.

How much does Phentaslim cost?

Phent costs $59.99 for 90 capsules.

How should I take Phentaslim?

You should take Phentaslim three times a day, once 20 minutes before breakfast and lunch and once in the late afternoon. It is not suggested to take Phentaslim after 5pm.

Can I take Phentaslim if I have a health condition?

You should ask your physician if you are under the age of 18, if you are taking prescription medications, have other underlying health problems, are pregnant, or nursing.

What do users like about Phentaslim?

Users liked that Phentaslim may curb appetite, increase energy levels, and there is a money-back guarantee.

What do users NOT like about Phentaslim?

Users don’t like how Phentaslim has multiple stimulants in the formula and how pricey it is.

How do I contact Phentaslim customer service?

You can contact Plentaslim customer service by emailing them at cs@phentaslim.com or by going to their contact page on the official website.

Is there an official website for Phentaslim?

Yes, there is an official website for Phentaslim.

Do you know how much of each ingredient is in the formula?

Yes, the amount of each ingredient used in Phentaslim are listed on the official website.

Does Phentaslim come with a guarantee?

Phentaslim has a 60-day money back guarantee.

You might ask yourself, is this product or that diet going to work for me? Truth is time will only tell as all individuals respond uniquely to weight loss results. Leptigen, is among one of the best products surfaced in 2016 to boost the metabolism and fat loss, noticing unbelievable weight loss transformations in consumers.

Phentaslim User Tips:

7 Top User Tips

Over the years, we’ve come to realize that Phentaslim users have something to say. After examining thousands of consumer reviews and comments we collected the most useful tips that may help you learn more about this product.


“It is important to remember that the weight loss will be gradual. It takes some time but it will work.” Jax


“I can’t take it as recommended or it makes me sick. I have to take each dose with food.” Sadie


“The instructions say to take one 20 minutes before each meal which is a really bad idea if you want to sleep. Skip the dinner dose.” Marie


“If you really want to see any decent results you will have to change the way you eat. Cut back on the total calories.” Linda


“You have to be so consistent when taking this. If I skipped a day I felt like I was starting all over.” Cora


“I though the energy boost with my first dose was nice so I took the rest as recommended. BIG mistake because I didn’t sleep at all. Now I limit myself to one in the morning.” Melinda


“These are super strong. I recommend people start with one a day to check their tolerance for them.” Bill

Phentaslim Scientific Abstracts:

Green Tea

There are some reports of the effects of EGCG (epigallocatechin-3-gallate) at a submicromolar level. However, most tests require concentrations of >10 or 20 micromol/L to test and demonstrate this effect. In humans, tea polyphenols go through sulfation, methylation, glucuronidation, and ring fission. EGCG’s peak plasma concentration is around one micromol/L. Thus, the potential significance of each of the proposed mechanisms for the prevention of cancer in humans is examined in light of up-to-date bioavailability data for tea polyphenols and the possible limits of animal models of carcinogenesis. New research efforts are sought out to discuss the misunderstandings of cancer prevention. [1]


Studies had shown that L-theanine had significantly inhibited blood pressure increase in a group of participants. Caffeine had a tendency for similar, yet smaller, effects of the blood pressure triggered by mental tasks. After the tasks, it was displayed that L-theanine had reduced tension-anxiety scores compared with placebo groups. It was concluded that L-theanine didn’t just decrease anxiety, but attenuates increased blood pressure in high-stress response adults. [2]


Magnesium has been reported to improve serum lipid profiles when intake is increased, offering an important role in cardiovascular diseases. Dietary magnesium has been suggested to help the prevention of stroke and is crucial for skeletal growth and development. It may also be important in the development of obesity, diabetes mellitus, and metabolic syndrome. There is additional data that suggest changes in lifestyle can benefit blood pressure control, help weight-loss, and improve chronic disease risk. [3]

Guarana Seed

Amiodarone’s plasma and tissue concentrations, as well as its major metabolite (mono-N-desethylamiodarone), were observed, measured and analyzed. A very noticeable decrease in the peak plasma concentration (73.2%) and the term of systemic exposure (57.8%) to amiodarone was discovered in rodents who were treated with amiodarone and Paullinia cup and. There had been an observance of tissue reduction as well. It was determined that the interaction of amiodarone and Paullinia cup and extract showed a significant decrease in amiodarone bioavailability in rats. [4]


Currently, niacin is available in three formulations – extended release, long acting, and immediate release. They possess a vast difference in their safety and efficacy profiles. Immediate release niacin is typically used three times daily and is accompanied by negative flushing, elevations in blood glucose levels, and gastrointestinal symptoms. The long-acting variety can be ingested just once per day, typically associated with substantially decreased flushing; however, its metabolism raises the risk of hepatotoxic effects. The last variety of niacin, which is also administered once daily, possesses an absorption rate intermediate between the others. Also, it’s associated with less flushing and gastrointestinal symptoms minus the increase of hepatotoxic risk. [5]

Phentaslim Side Effects:

Nowadays, weight-loss supplements are abundant. This doesn’t mean the natural solution is the one with zero negative effects. With each and every formula there’s a potential for an adverse reaction, while Phentaslim side effects are rare, it doesn’t necessarily mean they don’t happen for some users.


Nausea is the queasy, uncomfortable, sick feeling that typically precedes vomiting. Nausea creates an inclination to vomit as a warning system in your body. It may be trying to expel toxins or may indicate an inner ear or other disorder. It is most often associated with a viral infection or food intake.

What causes nausea?

The timing is everything. When appearing after a meal, it usually indicates an issue with digestion or the food you ate. If nausea occurs randomly, it could mean an inner ear imbalance or disturbance, inflammation of the stomach lining (gastritis), or ulcer.


Constipation is usually described as having one to three (in rare cases none) stools in a week. The body could experience hardened stool, straining or exertion while trying to make a bowel movement, and abdominal discomfort. [1]

What causes constipation?

Constipation is usually caused by the slow distention of food through any part of the intestine or colon. This can be caused by narcotic pain medications, anti depressants, or iron supplements.


Headaches are most commonly referred to as dull, sharp, or throbbing pain in the head and neck region of the body. The types of headaches are migraine, cluster headaches, and most the common, tension-type headaches which feel like extreme pressure in your skull.

What causes headaches?

Headaches are caused by overactive or problematic nociceptors that reside in nerves and muscles around the body. These nociceptors indicate pain and send the signal to the brain that something is wrong. Headaches could be caused by caffeine, stress, or overexertion of the body as well.


Dizziness is the feeling of faintness, or spinning. It’s an uncomfortable sensation that everything is whirling around you, even though you are stationary. It’s a feeling of being unsteady, weak, or having a false sense of motion. [2]

What causes dizziness?

Dizziness can have a wide array of causes including inner ear infections, motion sickness, or infection. Dizziness is most commonly caused by any disturbance in the eyes, sensory nerves, or inner ears. The fluid in the inner ear detects gravity and changes in motion. When the fluids are disturbed they create a false sense of spinning.

Phentaslim side effects are indeed rare, however some users have reported dizziness, headaches, and constipation, among others. In order to protect yourself from any potential negative effects, it’s always best to seek the advice of a doctor before taking any supplement, especially if you are pregnant or nursing, under the age of 18, taking prescription medications, or have any pre-existing medical condition.

To state the obvious, every individual person responds differently with weight loss products; all leading to different weight loss results, some successful, others not. One that has been scrutinized for its incredible results, Leptigen, has been clinically proven to accelerate weight loss, undue weight-loss plateaus and ignite the metabolism.

Phentaslim claims to be a "revolutionary diet pill" that's natural and allergen free. There are clinical studies offered on the official website and some do link some ingredients to weight-loss. There's no doubt the user could notice increased energy, but weight-loss claims are over the top and unattainable for the majority.

Phentaslim Ingredients and Supplement Facts

Serving Size: 1 Capsule
Serving Per Container: 90
Amount per Serving % DV
Green Tea 375mg *
Caffeine 270mg *
L-Theanine 225mg *
L-Carnitine 200mg *
L-Tyrosine 200mg *
Panax Ginseng 120mg *
Guarana Seed 100mg *
Magnesium 80mg *
Cayenne Pepper 50mg *
Niacin 20mg *
Zinc 15mg *
Black Pepper Extract 6mg *

Other Ingredients: Vitamin B6, riboflavin, thiamin, vitamin B12

We really researched the Phentaslim ingredients in order to provide the important details and specifics.

Green Tea Extract

Sometimes referred to as camellia sinensis, green tea is an unfermented variety that has been consumed in China and India for centuries. It is typically steeped in hot water and consumed for its health benefits.

What is it Supposed to Do?

There are quite a few different health benefits that pertain to green tea. For instance, this herb provides both caffeine (a stimulant) and catechins (antioxidants). These components have been shown to help boost metabolism and promote weight-loss. Furthermore, the antioxidants in this plant offer other benefits as well. They may assist with lowering bad cholesterol, improving immune system health, controlling blood sugar levels, and even preventing cancer. [1]

Clinical Research

According to the University of Maryland Medical Center, “Clinical studies suggest that green tea extract may boost metabolism and help burn fat. One study found that the combination of green tea and caffeine improved weight loss and maintenance in people who were overweight and moderately obese.”


Also known as 1,3,7-trimethylxanthine, caffeine is naturally found in plants such as coffee seeds, tea leaves, guarana, yerba mate and cocoa beans. It is a stimulant and mild diuretic. Many people get this ingredient daily from energy drinks, coffee and tea beverages, as well as sodas.

What is it Supposed to Do?

Often caffeine is added to weight-loss supplements to help suppress appetite, boost energy levels, enhance focus and stimulate metabolism. Since this ingredient is a stimulant, it affects the central nervous system. Some research has shown that it can aid with weight reduction by increasing thermogenesis. [2]

Clinical Research

PubMed.gov reveals that, “High caffeine consumers reduced weight, fat mass, and waist circumference more than low caffeine consumers; resting energy expenditure was reduced less and respiratory quotient was reduced more during weight loss. High caffeine intake was associated with weight loss through thermogenesis and fat oxidation and with suppressed leptin in women.”

Panax Ginseng

To start with, panax ginseng is a natural herb that grows in regions like Korea and northeastern China. It is also called Asian ginseng. This ingredient is found in countless diet supplements and energy drinks. It contains active components such as panaxosides and ginsenosides.

What is it Supposed to Do?

There are quite a few health claims regarding panax ginseng. For instance, this herb is supposed to help treat depression, combat chronic fatigue, improve memory, boost libido and treat erectile dysfunction.

Clinical Research

“People who take ginseng often say they feel more alert. Several studies report that Asian ginseng may slightly improve thinking or learning. Early research shows that Asian ginseng may improve performance on such things as mental arithmetic, concentration, memory, and other measures,” reported the University of Maryland Medical Center.

Guarana Seed

Also called Brazilian cocoa or paullinia cupana, guarana is a plant that grows in regions such as Brazil. This ingredient is found in various diet pills and energy drinks. It provides a significant amount of caffeine, which is a stimulant.

What is it Supposed to Do?

Typically guarana is added to dietary supplements for weight-loss to help boost metabolism, improve energy levels and enhance focus. It may also assist with appetite reduction.

Clinical Research

“Because caffeine is a stimulant that has been shown to improve mood and aid weight loss, guarana may very well also have these effects. As a weight loss supplement, caffeine may work best when combined with the polyphenol compounds in green tea. Combining guarana with polyphenols may have a similar effect,” says WebMD.

Amino Acids

Phentaslim contains three amino acids, which include l-theanine, l-carnitine and l-tyrosine. These are the building blocks of protein, which means they aid the body and muscles with repairs and maintenance.

What is it Supposed to Do?

Amino acids are included in this supplement to help with relaxation, improved cognition, fuel metabolism, muscle recovery, appetite suppression and increased energy levels. Some research shows that amino acids help fight arthritis, boost the immune system, lower cholesterol, reduce aging effects, improve muscle strength and support weight-loss.

Clinical Research

Researcher Robert Coker, PhD from the University of Arkansas for Medical Sciences says that, “Essential amino acids, included as part of a meal replacement, along with whey protein, improved the synthesis of muscle and led to a greater loss of fat.”

Bottom line, weight loss can be a long and tricky process. Among the best weight loss formulas surfaced in 2016, Leptigen promotes healthy benefits including accelerated fat loss, increase in energy and diminish weight-loss plateaus. It’s a dietary supplement highly regarded for weight loss.

Get Your Sample Today »
Dietspotlight Author
About the Author:

Summer Banks, a content strategist at Leptigen, has researched over 5000 products in the past 10 years. She has years of nursing training, experience as a manager responsible for 15 supplement brands, and completed coursework on Food and Nutrition from Stanford University. full bio.

Rating: 3.2. From 83 votes.
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User Comments

16 Comments on "Phentaslim Review"


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well i ordered my 1 month supply and i had received these tuesday just gone… i have taken one in the morning and one round my lunch time. i dont take the 3rd one as i wanted to adjust slowly to them..since being on these tablets i feel my body already reacting positivly to these . not only less appetite now but im going to the toilet more lol..sorry to go a bit gross but since going toilet more i notice old poo aswell leaving my body and my stomach doesnt feel as bloated aswell and actually looks flatter.. i do suffer with IBS badly and these do help with spasams for some reason (maybe with some of the herbal ingrediants)..im drinking 2 literz a day or even more now when before i would only drink a cup at night. i also feel more energy… i am a 38 year old woman and 2 kids.. full time job and housewife aswell… these tablets are defo doing something positive FOR ME… fantastic smile


I WISH I READ THESE REVIEWS BEFORE BUYING!! I had the worst nausea and jitters, my hands would literally start shaking uncontrollably! PLEASE PLEASE PLEASE, DO NOT BUY!!


Unfortunately I have a very negative view regarding Phentaslim: the product itself and the customer service. They promise to refund you within a certain period if you are not happy, which they haven’t. I did not lose any weight, moreover had some adverse side effects. Sorry I spent £100 for nothing.


How long before I would expect to see results?


You will not get any results. These really do not work. Waster of money


I beg to differ. I’ve been taking them for almost a week now. I’ve had loads of energy and am able to go for brisk, half hour walks.yes I can feel my clothes getting looser. I have been drinking lots of water and peppermint tea and eating healthy, small portions throughout the day. Feel fine so far. It’s like anything. Can work for some people, maybe not others. I’ve also read many good reviews on other sites.


i really like it im so happy im losing weight finally happy happy

Your Name

What is the address to return products????????????


TI have been taking this for two weeks with no weight loss. I have only been taking one a day because I did not want to be kept awake at night.

Your Name

Totally waist of my money .

No change

Took 30 day supply didnt have more energy and didnt help with weight loss even though i cut my portion size down ate healthy and excersised 5 days a week! wouldnt waist money buying it!


Totally waisted my money. Very disappointed. Didn’t reduced my appetite, didn’t speed up my metabolism in fact increased my appetite and gave me constipation. I do not recommend this produc!!!

Breda Russell

Can I have the address to send back products and reclaim my MONEY……..


I have to say when I particular read these reviews I thought that it sounded great. I took this just over one week and have to say not a good experience, jitters, sick feeling. I really thought after all the reading that this would not give you these type of sensations. I had a horrible feeling of sickness and jitters throughout my body to the point my hands were shaking. Definitely didn’t reduce my appetite but I think that the sickness was suppose to maybe put you off food. I would not recommend this product at all in any positive way.

Breda Russell

Never again.Very bad jitters and trembling.No weight loss whatsoever but nausea and no sleep.I am returning mine and I will demand a refund…..


Their website states they have a 100% money back guarantee, but beware!!! These diet pills DO NOT work. Once you buy them, you own them because they will not refund your money as they advertise. Don’t waste your money.