Phentaslim In-Depth Reviews

phentaslim 2021 formula

Phentaslim is a fat burner and appetite suppressant that asserts that helps people lose weight through a metabolic rate boost.

It accelerates the rate by which your body turns calories into energy and also achieves fat burning through thermogenesis; by increasing your body inner temperature, you spend more calories than normally.

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As of July, 2015 Phentaslim has been upgraded to the new and improved formula for the maximum power and effectiveness.

As of 2022, the formula has been further enriched and is now 100% vegan-friendly.

Who Stands Behind?

This supplement is created by the company called Optimum Nutra, that’s been established in 2011 to formulate top grade dietary supplements for health and weight loss.

official website optimum nutra

While the company is comparatively young and hasn’t yet established themselves as a relish in the industry, what seriously make us appeal to them is highest quality of ingredients, pharmaceutical GMP-certified manufacturing process, and transparent customer-friendly business practices.

As we checked their 2 other supplement brands, we found that only scientifically tested components are used, and the formulations are pretty unique compared to other weight loss tablets available today.

How Does It Work?

Phentaslim lists over 12 different compounds and extracts in its ingredient list which target different weight loss aspects, fat burning, appetite suppression, metabolism boost and energy increase.

This formula promises to help both men and women lose stubborn fat and control their appetite simply by taking the one capsule twice daily, 20 minutes before breakfast and lunch.


The slimming pills include the following extracts and natural compounds which have been clinically tested for weight loss:

Capsicum Extract (Cayenne) (50 mg) – stimulates thermogenesis which might lead to weight loss, also improves the other ingredients’ absorption

Green Tea Extract (375 mg) – stimulates fat oxidation and thermogenesis

Guarana Seed (100 mg) – energy boosting stimulant, that also helps with appetite suppression

Caffeine (270 mg) – boosts energy, mood and alertness (note that daily caffeine intake from the pills is close to the daily recommended dosage, consuming extra caffeine from drinks may result in overdose and side effects)

L-Tyrosine (200 mg) – helps with sustained energy levels and fights post-workout fatigue

L- Carnitine (200 mg) – increases lean muscle mass and promotes fat oxidation

L-Theanine (225mg) – reduces mental and physical stress, boosts mood and improves cognitive functions

Panax Ginseng (120mg) – boasts of multiple positive effects on health and well-being, including physical stamina and mental endurance, boosting the immune system and helping to stay active and alert.

Black Pepper Extract (6mg) – also known as BioPerine, improves the digestion of all other substances, on it’s own helps to block fat calls formation, and reduces fat levels in the blood.

Niacin (20mg) – aka vitamin B3, used to improve cholesterol levels, and lowering the risks of cardiovascular diseases.

Magnesium (80mg) – helps to prevent high blood pressure and reduce inflammation risks

While all these ingredients have been clinically proven to assist with weight loss each one in its own capacity, the actual dosage of each ingredient seems to be sufficient to promote weight loss.

In addition, it’s a is primarily a stimulant-based weight loss supplement. Guarana seed, Green Tea and Caffeine Anhydrous all seek to increase energy levels and alertness, and 5-HTP1 to induce appetite suppression and improve mood.

Phentaslim Side Effects

Since this supplement contains a pretty number (17 to be exact) of ingredients and some of them are stimulating metabolism, some of the people may experience side effects if they have sensitive nervous system and/or skip the recommended usage as stated on the bottle.

Here I’ve collected the potential side effects that might appear from using some of the ingredients alone (not in the exact Phentaslim formula), just FYI.

  • Panax Ginseng could cause an increase in blood pressure in patients with the problem.
  • Caffeine could cause an excess of heat generation, especially during summer. But you could overcome the problem by consuming more water and water fruit juices. 
  •  Guarana seeds may cause sleeplessness (insomnia) in some people who could be allergic to the ingredient. You have to consult your family physician before consuming Phentaslim. 

Some other people also reported nausea after starting taking the supplement.

I would add that the supplement is formulated to contain only the safe dosages of each ingredient. However, each of us is unique so some people may react differently to the supplement.

Sucess Stories

The official Phentaslim website features successful dieters’ testimonials. However, these read rather generalized and don’t offer much personal information so as to check for credibility.

One of the FB posts I’ve come across was shared by a UK real customer who told he was using Phentaslim with his wife and they got great results.

Phentaslim customer review on Facebook

However, he did not share before and after pics and exact lbs lost, just a story.

It can be illustrative though, to see that the supplement doesn’t do all the work itself, but provides a boosted fat burning along with the diet control.

Positives And Negatives


  • 100% Natural (Contains NO banned or hard stimulant components)
  • Works for men and women
  • Free international shipping options for any purchases
  • Developed in GMP-certified labs
  • 30-day money back guarantee
  • Clinically-tested weight loss ingredients


  • Not suitable for caffeine-sensitive individuals
  • May interfere with prescription medications (requires GP consult)

Safety of Use

Phentaslim uses 100% natural compounds and vitamins so it’s safe to use. By taking Phentaslim you substantially increase your daily caffeine intake.

So if you’re caffeine sensitive you might wish to control your total caffeine intake from other sources such as green tea, coffee and power drinks.

Increased heart rate, palpitations, sleep disturbance and other caffeine-related side effects might be experienced if you don’t monitor your caffeine intake.

Pregnant, nursing women, people with BMI less than 18.5 and teenagers shouldn’t take Phentaslim. Anyone with a known condition or people on prescription drugs should first consult their physician before purchasing it.

Phentaslim contains gelatin so it’s not suitable for vegetarians either.

Phentaslim Frequently Asked Questions

Is Phentaslim FDA approved?

No, it’s not FDA approved. Since Phentaslim is a dietary supplement and not a drug, it doesn’t require FDA approval to be available for the people.
The supplement hasn’t been rejected by FDA either and it doesn’t contain any banned or harmful ingredients.

Is Phentaslim Safe To Use?

In general, it’s safe to use unless you have some specific health conditions like increased blood pressure, sensitive nervous system. In this case, there may be some side effects. It’s not recommended for pregnant or lactating women and people below the age of 18.

Is Phentaslim Gluten Free?

Yes, it’s 100% free of any form of gluten.

Can I take Phentaslim With Alcohol?

It’s advisabe to limit or quit your alcohol intake if you take this supplement. Since both Phentaslim and alcohol affect your nervous system, there may be some adverse reaction.
Also, alcohol is a source of “empty” calories, and it may interfere with the appropriate ingestion of the supplement.

Is Phentaslim Safe With Antidepressants?

Only the doctor who prescribes antidepressants can answer this question! Phentaslim activates your sympathetic nervous system while some antidepressants try to suppress it’s excessive activity. Please let your physician know if you’re going to take this supplement – this is very important.

Can I Take Phentaslim if I Have Diabetes?

There are no specific ingredients that negatively affect your blood sugar levels, but if you take medications, always consult with your doctor before taking the supplement.

Is Phentaslim OK With High Blood Pressure?

On a safe side, it’s not OK. Please consult with your doctor or consider non-stimulant fat burning supplements.

Verdict – Is Phentaslim Worth Taking?

The supplement is marketed as a fat burner and appetite suppressant, rather it’s a complex natural combination of vitamins, minerals and amino acids to support energy levels, and stimulant-based components to promote calorie expenditure and suppress appetite, which combined, may help you burn excessive fat and lose weight.

With only clinically researched ingredients included in the formula, Phentaslim can be recommended as a great fat loss aid unless you’re sensitive to stimulants like caffeine, or take any prescribed medication.

Where To Buy Phentaslim

buy Phentaslim direct here

The product can be purchased from the official website and comes with a free worldwide shipping for any orders.

If you see any other store selling it, be aware that this supplement is only available from the official website (screenshot here). Don’t risk ordering counterfeit product that doesn’t come with customer support and guarantees.

A one-month supply bottle comes at $49, while the most popular 3+(2 free) month supply is $147.

As for the Phentaslim coupon codes – please check the official website, they do offer discounts from time to time, but coupons are not available outside.

You can pay with credit card, Paypal or Paypal Credit. Each payment is secured and protected. The company never re-bills their customers like many shady online retailers still do. So your purchase is risk-free.

Each order is backed by unconditional 60-days money-back guarantee.

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Stanley Burnett
Stanley Burnett
My goal on this website is to provide you with unbiased reviews of slimming supplements in the UK market today, and give recommendations based on years of experience in fitness, health and supplements industry. I'm a supplements nerd, fitness junkie with over 10 years of experience in the field of fat loss, muscle building and overall healthy lifestyle. Click to read more about me.