Phentaslim fat burner
Fat Burner
Reviewed 2023


A superb thermogenic formula for effective ‘fat-burning’ and increased energy. It’s our top pick for weight loss.

Updated Feb 28, 2022.
Published Sep 23, 2019.
Dr. Krystal Crawford, ND, MS
Medically reviewed by Dr. Krystal Crawford, ND, MS, written by Rachel Butler.

Our Verdict

Phentaslim is a powerful metabolism booster. This means it will work to raise your metabolic rate. All sounds like too much science? Probably. Put simply, a faster metabolism is the perfect way to lose weight and to lose it properly.

We’ll get straight to the point: for ‘fat burning’, we’re yet to find a better product.

We’ve loved Phentaslim ever since it was first released many years back. It’s now better than ever, having been revised to make it vegan-friendly. All considered, there’s very little not to like about this weight loss supplement.

Those looking for a quick-fix, no-effort needed weight loss miracle will remain disappointed. There are no gimmicks to be found here. This is a genuine product with lasting results in mind.

If you’re serious about losing weight and are ready to ditch those unhealthy bad habits, this product could be your new best friend.


  • Over 229,308 customers
  • Uses natural ingredients – no chemicals.
  • Vegan friendly capsules.
  • Effective metabolism boosting formula.
  • 60-day guarantee.


  • Contains caffeine. You might need to reduce intake elsewhere – afternoon coffee?
  • Need to buy more for lower pricing.
For the latest offers and best pricing:
Phentaslim Website

Phentaslim – A trusted fat burner.

Feeling fed up of always trying and not often succeeding when it comes to losing weight? We wouldn’t blame you if you’re feeling deflated. Losing weight is hard work.

No doubt you’ve also noticed there are lots of weight loss products claiming they can help you shift the pounds. It’s unfortunate that most of them are as they seem: too good to be true. No-effort weight loss tablets and bits of cotton paper you stick to your belly to burn fat; what nonsense.

Thankfully, Phentaslim is different.

Phentaslim assists with weight loss by raising your metabolic rate and boosting energy. This helps your body to use more calories and reduce body fat. It also provides vitamins and minerals that can help with alertness and concentration. You can read about the ingredients further down this page.

Dieting is tough on the body, and this supplement has been crafted to help all round.

Phentaslim is an established product and has been on sale for a decade.

Does this matter? Yes. We’ve seen so many products come and go but only a few that stick around. It’s difficult enough finding a product that works without having to worry if it will still be available in six months’ time. Phentaslim, in our opinion, can be relied upon.

Made by Optimum Nutra, and now updated to be vegan-friendly, it is manufactured in a certified facility in the U.K. This assures safety and quality, since regulations here are very strict. This is not a dangerous Chinese knock-off, this is the real deal.

There’s also a 60-day guarantee. Quite simply, if it doesn’t work for you, send it back for a refund.

How to Take Phentaslim

Take Phentaslim three times a day. One capsule in the morning, one at lunch, and the final one early in the evening. Each capsule is taken with a glass of water. Pretty straightforward.

If you’re exercising, and for better results, we would recommend using Phentaslim half-an-hour or so before doing your activities. It will provide you with an energy boost at the perfect time, helping to burn through even more calories. Don’t use an extra capsule, just reschedule one of the three taken daily.

Phentaslim fat burner

Phentaslim key features

Losing weight is one thing, but dieting can sometimes cause other problems. Fatigue and low nutrient intake are common side effects of dieting.

Phentaslim keeps these in mind and makes them as much a part of the product as weight loss.

Phentaslim’s basic premise is to:

  • Raise Metabolism – Ramp up your metabolism so that you can burn more calories and increase fat loss.
  • Boost Energy – Boosts energy levels without that crash and burn feeling, so you’re ready for anything!
  • Utilise Body Fat – Burn though your fat stores by using them as a source of energy.
  • Support Wellbeing – Vitamins and minerals for cognitive and all-round immune system support.

Phentaslim ingredients – Formulated to perfection.

Phentaslim is made using premium-grade ingredients, all of which are stated on the label. This is not a mysterious ‘proprietary blend’, which is simply nonsense that we see all the time. It’s your body, you should know every ingredient that’s going into it.

It’s a fine combination of ingredients in the right quantities.

You’re getting all you need for raising your metabolism to burn fat, and additional vitamins and minerals to help avoid the pitfalls of dieting.

The ingredient quantities provided below are per three-capsule serving.

Does Phentaslim work? It’s a thumbs up from us.

We’re confident enough to say, yes, it does work, especially when you use it correctly.

All fat burners work best when used in combination with a limited-calorie diet. By limiting your calorie intake, your body will have little choice but to use stored fat for energy.

Exercise is important, too. Even just something gentle will be beneficial. You’ll get faster results with exercise.

Phentaslim will raise your metabolism but it’s up to you to utilise it. Go for a walk!

We tested the product for a month.

During this time, we found our energy levels improved and we certainly felt better for it.

We also noticed some appetite suppressant qualities during use. This isn’t stated as a benefit of the product so it came as a pleasant surprise.

In the office, Clare, from admin, used the metabolism boost to improve her running distances. Clare says she definitely noticed the difference. Although relatively healthy anyway, Clare’s example demonstrates the potency of the product.

John, who has written his own review over at Muscle Watchdog, was aiming for weight reduction. He extolls how effective the product is for helping reduce his middle-aged waistline:

I’m impressed with Phentaslim and the manufacturer, Optimum Nutra. There’s no question, this supplement will give you awesome energy and targets your body fat.

Based on our evaluation period we would expect Phentaslim to work as claimed. How refreshing it is not be sold a far-fetched dream. Be reassured, this is no keto diet scam.

Feedback from verified customers is reassuring:

I ordered this product mid-April and am really liking it so far! Have lost noticeable weight (that people comment on). I do exercise regularly anyway so haven’t changed anything there, it’s just given me a much needed boost. The only thing I will say is that – as a big caffeine drinker myself – do not drink coffee while taking this product, at first I couldn’t sleep/was feeling a bit jittery. However when I cut the coffee down that all stopped! Good product if taken correctly!

I received my order in the mail super fast which was awesome. Best of luck to everyone who takes these, they’re great!

So after a full two-month course on these pills, I am very happy to announce that I have lost two and a half stone in two months! I would recommend these to anyone hoping to get a head start on their weight loss as the extended energy, fuller feeling of stomach and the ease of use make these HIGHLY commendable.

Feeling massive improvements in my energy levels. Using these before exercise as well as before eating. More energy = being more active = losing weight faster = feeling great!!!

I only use one pill now in the mornings to wake me up. Really feel the benefit on my walk to work, gets me moving like a machine. Used before to lose a bit of weight and worked v well. Wanted to keep on using but don’t feel I need the full daily serving anymore.

Negative feedback tends to mention the caffeine used in the product:

Not for me. I knew it contained caffeine but thought I’d it anyway. Too strong for my liking. I’ve tried decaf products before but they don’t really do much.

Yikes! Are we to never sleep again? Definitely do not use at night you’ll be awake into the small hours.

To be fair to the manufacturer, the label does state not to use the product late in the day. Consider yourself told.

Buying Phentaslim

Price: Varies / Money-saving packages available.
Format: Vegan-friendly capsule, size 0 (easy-to-swallow).
For the latest offers and best pricing:
Phentaslim Website

Phentaslim side-effects – Nothing much to report.

Phentaslim is a great product. This doesn’t mean it’s the right one for everybody – this, though, would be something of an unreasonable expectation.

There’s always the potential for some side-effects. If you are taking prescription medications you should consult with your doctor before using any supplements. This we would advise for any product.

Those sensitive to caffeine may wish to consider something milder. Phentaslim does contain theanine, which can help to limit caffeine side-effects.

It may help if you limit caffeine from other sources. Partial to tea and coffee? Perhaps switch to a decaf blend. Chocolate also contains caffeine, but you’re supposed to be losing weight – put the chocolate down. You can read more about caffeine in our guide, here: Wake Up and Smell the Caffeine.

The manufacturer suggests those who find the product too strong may wish to use a reduced serving size, by using two capsules per day instead of three.

CAUTION: Always swallow the capsules with water. Do not take if pregnant or nursing. If you have any medical conditions or are taking any medication, consult your doctor before use. Not suitable for anyone suffering from any heart-related health issues, including, but not limited to, high blood pressure. Not suitable for those under the age of 18.

Conclusions about Phentaslim

Overall, we’re impressed with both the product and the manufacturer.

Phentaslim itself has been well thought through. You’ll not often come across a product like this. This is not sold as a secret, mystery formula. There are no gimmicky, faux brand-named, nonsense ingredients either. Everything about Phentaslim is fully disclosed.

Optimum Nutra offers free shipping and a 60-day guarantee. We contacted customer service with some random questions and received polite and informative responses. The product website is genuine and free from misleading claims.

In terms of Phentaslim’s effectiveness, we know from our own in-house testing that weight loss can be expected when it is used as directed. Third-party customer testimonials also back this up.

The simple fact is Phentaslim can definitely boost your weight loss.

Phentaslim fat burner

Phentaslim gets full marks from us. If you have realistic expectations for losing weight this product is made for you. The pricing is good, the quality is high, there’s a guarantee, and shipping is free.

Official Website

Disclaimer: Our reviews and investigations are based on extensive research from the information publicly available to us and consumers at the time of first publishing the post. Information is based on our personal opinion and whilst we endeavour to ensure information is up-to-date, manufacturers do from time to time change their products and future research may disagree with our findings. If you feel any of the information is inaccurate, please contact us and we will review the information provided.

Have Your Say

10 comments on 'Phentaslim'

  1. Hi.

    I’m nearly 30 and starting to worry my metabolism is slowing down like scientists say it does. Getting to that point where weight gained might be permanent if not dealt with.

    Last few years I’ve fallen into the trap of too much Netflix and sofa.

    I Used a bottle of this during lockdown and I lost 5lbs. I think it relies on having determination as well. I tried to stick to doing 10,000 steps a day as my exercise. Some days I did more. One day I did nearly 16,000! Must have been a nice day that day!

    I didn’t really suffer any side effects. Sometimes felt a little bit of a buzz but in a good way. I did cut down on coffee and had more water. I’m partial to a mocha which is probably the worst type of coffee for a dieting gal! Need a treat every now and then, though.

  2. Hmm. I’m interested in trying this.

    I’ve tried many other pills and just get left feeling disappointed. Here’s hoping this one is different. I’m not expecting bikini body results (would be nice though!) just something to make me feel like I’m going in the right direction.

  3. I actually wouldn’t mind a subscription service for these pills. I asked the company and they don’t offer one. I have to place a new order whenever I need another bottle.

    Been using it for four months now and have lost two stone without putting any of it back on. Results are slowing down a little but I expected this since it’s always the last bit of extra weight that’s the hardest to lose.

    I agree with your review. * * * * *

  4. My new gym buddy!! Energy boost great for my workouts. Noticed I’ve lost some extra body fat as well since started using

  5. These do not work at all I havent lost a pound since i started on them last week. When i informed the company they dont work they told me i had to exercise as well! whats the point! might well just not buy them and exercise instead. pointless.

    1. You cannot just take a pill and expect to lose weight. Such a silly comment to write. This is a supplement. Look up the word supplement. I imagine you’re one of these people that complains about everything. Boiling water not hot enough. Sigh. Goldfish too orange. Sigh. Like the review says, these boost your metabolism but it’s up to you to make use of it.

  6. Tried this last year before it went vegan. It helped me drop a stone before my holiday. Deffo boosted my confidence on the beach. Not claiming I looked like a model, but it’s that thing of knowing in your head you look better than you did before. Made me feel great. Coming back for round two now. Hoping the vegans haven’t ruined it like they do with sausages!

  7. Can I use this with antidepressants like lexapro clonezapam lamotrigine and melatonin? Is this product safe for me to use as I am desperate to lose weight?

    1. Hi Bianca. You should really discuss this with your doctor. Don’t just ask anyone online, they’re not qualified, it’s just asking for trouble.

      Ask your doctor, please. I was on medication for anxiety and asked about diet pills (not phentaslim), I was told the risks would be small if any and that if I took them and felt weird I should stop. I took them, didn’t feel weird but had to stop (because of the price). I’m trying now to lose weight the long hard way instead. Less food, more moving.

  8. I’ve been using these for a about three months now and things look promising.

    Truth is it hasn’t been easy but I’m making progress. Three months ago I weighed 124 kgs (19 stone 6, 274 pounds). I’m 34 years old and look a mess. So I’ve changed my diet, changed my lifestyle. Less carbs and sugar (basically, less junk food), more proteins and salads and clean foods. For exercise I take a daily long walk, usually up to 5 km. Takes me about an hour and half to do. Not ready for jogging yet but hopefully will be soon. Planning on keeping it up even when the nights get long and dark.

    Using Phentaslim as directed on bottle before breakfast, lunch and dinner. It helps to keep me going especially when my motivation is low. Can notice the extra energy especially on my walks. I usually do the walk late afternoon and sometimes at night after dinner when usually I’d be slouching in front of TV.

    My weight is currently 117 kgs (18 stone 5, 259 pounds). To me, this is a lot of weight lost. I haven’t lost any weight for years its been creeping up and up. In 2017 I was 17 stones. In 2018, 18 stone. Last year, 2019, 19 stone. See the pattern? 2020, 20 stone? Not a chance!

    So happy to finally be in reverse. Hoping it continues this way. My dream weight is 12 stone. I’m aiming to do it gradually bit by bit. Thanks.

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