Updated May 8, 2019.
Published Dec 21, 2016.

PhenRX is advertised as an OTC alternative to prescription diet pill Phentermine, but it actually looks to be a quite dangerous product with some sketchy ingredients – and we don’t even know the quantities. PhenRX may well give you a bit of a buzz (due to the stimulants), but there is also a risk of side effects – particularly if you have any issues with your heart or blood pressure.


  • Some positive customer feedback


  • No ingredients list provided
  • Contains potentially dangerous ingredients
  • Deliberately confusing explanation about how it works
  • Dubious money-back guarantee
Phen RX
PhenRX is a fat burner that is supposed to increase your energy levels as well as help you burn off fat fast. It comes from Nexgen Biolabs a USA based company that specialises in OTC copies of prescription meds and the supplement is available as a diet pill or as a weight loss patch.

We take a look to see what it is all about.

PhenRX Overview

What you need to know about PhenRX

We are not very impressed with PhenRX.

It contains some dodgy ingredients in unknown quantities and you may find that side effects are an issue. You should certainly avoid it if you have any health issues, especially those relating to heart and blood pressure.

We are not very impressed with the so called guarantee either. This is advertised but without any details about how to claim it, we feel it is unlikely that you will obtain a refund if you are not satisfied.

What are the side effects of PhenRX?

PhenRX will certainly not be safe for everyone and if you have a medical condition relating to heart or blood pressure or you are taking prescription medication you should definitely avoid.

Many Watchdog readers have mentioned side effects including; headaches, vomiting, nausea, heart palpitations, jitteriness, anxiety, increased heart rate, elevated blood pressure, increased risk of stroke or heart attack., insomnia, and upset stomach.

According to Nexgen side effects are rare and may include dry mouth and sleeplessness.

How much does PhenRX cost?

If you buy PhenRX direct from the Nexgen Biolabs site it is expensive:

  • 1 x bottle of 30 capsules costs $39.99. Shipping is calculated at the point of sale.
  • 1 x packet of 30 weight loss patches costs $29.99.
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PhenRX Key Features

PhenRX is a supplement that has copied the name of notorious diet pill Phentermine so just from this alone we can assume that it is going to be strong!

This supplement is most commonly taken as a diet pill but is also available as patch that you stick to your skin and wear in the same way as a nicotine patch.

PhenRX Key Points

  • Made by Nexgen Biolabs
  • Comes in 60 capsule container – one month’s supply
  • No money-back guarantee offered

PhenRX contains a lot of stimulants. These include Trimethylxanthine – which is actually just a fancy name for caffeine, a mood stimulant called Beta Phenylethlamine, also known as PEA, which is believed to stimulate the brain’s feel good chemical dopamine.

It contains Synephrine, a chemical that increases the metabolism in a similar way to banned substance Ephedrine and increases heart rate and blood pressure. It contains Yohimbe – a chemical that is believed to stimulate sexual and athletic performance.

Other ingredients include Chinese plant extract Schizandrol – a stimulant that kicks in a few minutes after taking and can last for up to an hour, Dimethyl 4 another stimulant with a similar way of working as ephedrine and trace amino acid Tyramine.

How to Take PhenRX

Take two capsules a day with water.

It is not advisable that anyone takes this supplement for too long or if there are any medical issues. PhenRX could be dangerous for some people as it will increase the heart rate and blood pressure and it may cause a range of mainly heart related side effects.

Nexgen Biolabs have past form in marketing supplements that copy prescription drugs and are high in stimulants. PhenRX is supposed to be similar to Phentermine – a weight loss supplement with numerous side effects and only available under prescription. In addition, one of their most popular supplements is AdderRX a copy of Adderall – an addictive prescription drug that contains amphetamines and is used to treat ADHD (attention deficit hyperactivity disorder).

PhenRX Concerns:

  • Incomplete ingredients profile – you do not know how much of any ingredient you are taking
  • Contains ingredients that increase heart rate and blood pressure
  • Probably will not help weight loss once you get used to the effects

Adderall misuse is rife in US colleges where students use it to boost mental performance and study grades. Nexgen Biolabs have been criticised for handing out free samples of AdderRX on US college campuses.

Other Nexgen Biolabs supplements include Jet Rush aimed at party animals and speed freaks and SlenderFruit-7.

As with all weight loss supplements, just because PhenRX is legal, does not mean that it is safe.

What does PhenRX claim to do?

There is nothing subtle about PhenRX. You will notice this supplement and if you are looking for a stimulant buzz, you have probably found what you are looking for here. According to Nexgen Biolabs, PhenRX it is their best-selling and strongest weight-loss formulation.

Stimulants are popular for weight loss and there is evidence that they work. Stimulants increase the speed of the metabolism and as a result increase calorie burn; they can give you added energy and motivation to exercise.

According to the advertising, this comes down to six key benefits:

  • Extreme weight loss
  • Maximum strength appetite suppression
  • Energy enhancement & mental focus
  • Significantly reduce BMI (body mass index)
  • Targets fat and lipid metabolism on stubborn problem areas
  • Enhance metabolic function and fat burning

Does PhenRX work?

PhenRx contains stimulants and ingredients that will increase your heart rate and blood pressure. You will probably notice an energy buzz after taking but there is nothing here that specifically targets weight loss beyond the stimulant effect.

The capsule contains just 377 mg but we do not know the ingredients breakdown. It may be mainly caffeine (an average coffee contains 100mg per cup) but whatever it is you will probably notice it.

PhenRX is a very basic looking supplement. It contains only stimulants and there is evidence that that taking stimulants can help increase weight loss. The downside is that this method of weight loss will cause side effects so will not suit everyone.

Many Watchdog readers have contacted us complaining about side effects following taking the capsules or the patches.

phentaslim bottle
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Read the Watchdog Phentaslim review here.

PhenRX Ingredients

PhenRx is a diet pill that contains stimulants and not much else. The company are cagey about their ingredients and do not provide a full ingredients list, beyond a fuzzy picture of a label that is impossible to read.

When we did find one we saw that this is a propriety blend so lacks an ingredients breakdown. This means we can’t give you ingredient quantities.

However each capsule is equal to one serving and contains 377mg:

  • 137 Trimethylxanthine: This is another name for caffeine, the world’s favourite stimulant. It can be effective as part of a weight loss diet because it raises the speed of the metabolism.
  • Synephrine HCL: This stimulant raises the heart rate and increases blood pressure and is billed as a way to increase the metabolism in place of banned substance ephedrine.
    Synephrine sometimes called Bitter Orange or Citrus Aurantium features on WebMD’s danger list. It is not safe and can cause heart palpitations and a whole range of side effects. It has been linked to causing heart attacks and strokes. See our previous investigation on Synephrine HCL for more information.
  • Schizandrol: Sometimes used in body building products and is also an ingredient in other NexGen product JetRush. This Chinese plant extract has a stimulant effect within a few minutes of taking. The short term high will last around an hour and the side effects have not been fully investigated. It may be unsafe. Does not appear to have an application for weight loss
  • Beta Phenylethylamine (also known as PEA): is believed to stimulate brain chemicals serotonin and dopamine. It causes a short-lived high effect but is quickly metabolized. It is this high that makes it attractive as a supplement but the effect often lasts only a few minutes.
  • Yohimbine: Another one on the danger list, Yohimbe is believed to improve sexual and athletic performance but lacks evidence to prove this. Reported side effects include blood pressure changes, heart beat irregularities and heart attacks.
  • Dimethyl 4: Stimulant believed to be a safe alternative to ephedrine but no evidence that it is actually any safer. Sometimes used in medication for attention deficit disorder and weight loss but there is no evidence that it works. Can raise the heart rate and blood pressure.
  • Hydroxy Phenylethylamine: Also known as Tyramine a naturally occurring trace element from amino acid tyrosine. Can cause side effects in some people and is known for creating the “cheese effect” – the migraine that some people experience after eating cheese. May increase blood pressure. Source:

PhenRX Side Effects

Phen RX will certainly not be safe for everyone and if you have a medical condition relating to heart or blood pressure or you are taking prescription medication you should definitely avoid.

Many Watchdog readers have mentioned side effects including:

  • Headaches
  • Vomiting
  • Nausea
  • Heart palpitations
  • Jitteriness
  • Anxiety
  • Increased heart rate
  • Elevated blood pressure
  • Increased risk of stroke or heart attack.
  • Insomnia. You may not be able to sleep at night
  • Upset stomach

According to Nexgen side effects are rare and may include;

  • Dry mouth
  • Sleeplessness

Avoid if pregnant or breast feeding. Do not take PhenRX if you suffer from a heart condition or have high blood pressure. Do not take if you are sensitive to stimulants or suffer from mental problems. Avoid if you have any type of medical condition related to the thyroid. See your doctor before taking if you are on medication, because of the risk of drug interactions.

PhenRX Customer Feedback

Yes and it is a mixed bag. Many people are very pleased with this supplement and feel very positive about it.

A big thumbs up from me, I dived in to try something new and I’m very happy
with the overall outcome, I highly recommend these to lose weight

said one customer.

Despite some customers reporting an increase in appetite, this is not the same for everyone;

This is the first weight loss product we’ve tried that actually seemed to work… This is a pretty strong stimulant, so if you are not used to them, be careful

Not everyone is as pleased.

I took these for about 4 days and had to stop. It felt as though my heart was affected badly… racing at times and a feeling of pressure. In any case, it may be good for some, but obviously not for me….

A typical negative review came from this customer;

I felt no different taking this product. It has not given any energy nor weight loss. I would not recommend it, save your money.

PhenRX Money-Back Guarantee

According to the Nexgen Biolabs advertising, all purchases from the website are covered by a 30-day guarantee.

This sounds good but in our opinion, Nexgen Biolabs are unlikely to honour this claim. There are no details about how to claim the guarantee such as the return address, whether you need to obtain a RAM (return number) or any other criteria.

This lack of information in the terms and conditions makes us believe that the guarantee is there for decoration only and may not be honoured should you wish to claim a refund.

Our advice about the guarantee? Don’t hold your breath. You are very unlikely to get your money back.

Where To Buy PhenRX

Phen RX used to be on sale via Amazon and similar websites but these days it seems to be mainly on sale via the discount site Groupon where prices will vary.

One deal we have seen is a two pack package (2 x 30 capsules) of Phen RX for $17.99 plus shipping costs.
We have also seen 1 x packet of Phen RX patches (30 days supply) for $19.99 plus shipping.

If you buy Phen RX direct from the Nexgen Biolabs site it is more expensive:

  • 1 x bottle of 30 capsules costs $39.99. Shipping is calculated at the point of sale.
  • 1 x packet of 30 weight loss patches costs $29.99.

Watchdog Verdict

All that said, there is some genuine positive customer feedback for PhenRX. Some customers have found that the capsules and the patches have helped support weight loss so this supplement is obviously doing something for some people.

If you can find some cheap deals on the Groupon discount site it won’t actually cost you much to give this supplement a try. Then again when there are much better alternatives on the market we would question why waste your time.

Despite this, we cannot recommend this supplement. In our opinion it is dangerous and if you are one of the many people who suffer from side effects, even a discount price will turn out to be a waste of money.

How does PhenRX compare to Phentaslim?

CriteriaPhenRX ComparisonPhentaslim comparison
Clinically Proven Ingredients
Side Effect Free
Positive Customer Reviews
24/7 Support
Money-back Guarantee

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

47 comments on 'PhenRX'

  1. Did some of a bottle. Did very little except make me temporarily energetic, then crash. It can make me anxious and irritable. I’m a “talker” so this increased my chatty Cathy tendencies with the nervousness. Would not recommend to a friend or anyone with any health issues. I have DII and feel this product may be dangerous for me. Have had heart issues until I had by pass and CABG, so I’m not a good candidate for products like this anyway. Too hard on the nervous system. Great for cleaning the house!

  2. Phen Rx patches seem to help but when I take the pill i seem hungry all the time and get nauseated very badly.

  3. I just started phenrx 3 days ago. Since then I have felt more fatigue than usual and I actually think it increases my appetite. Maybe I need to try it longer….

    1. I feel like my appetite has increased from taking the pill but patches seem to work better for me.


  5. Started today, a little jittery/anxious but not really hungry at all. I put the patch over my navel but it didn’t stay very well. I am going to put it below or above my navel; I think it’ll adhere much better as your belly button does produce moisture throughout the day and would obviously interfere with its ability to stick for 24 hours. I AM going to sleep (right now) with the patch on. I think (maybe hope) I’ll be able to sleep. If not, I’ll be using it for the 18 hours I’m awake and go from there. I’m optimistic at this point and look forward to positive (I hope) results.


  6. I am trying my patch today for the first time. I didn’t want it on my abdomen, so I put in on my buttocks area. I hope it works….I am worried about getting jittery.

  7. I got the patches. Placing it around my Navel doesn’t work for me adding. Bondage arou the corners didn’t help either. any other suggestions. Thanks

  8. Yes it does have a smell. Mine also came in the same packaging. I started yesterday. My stomach feels like its tingling but no issue.

    1. Are you still doing the patches? What side effects did you have? How much weight did you lose?

  9. Hi Judy – I ordered them also (they arrived yesterday)and was VERY surprised they were Outside the box…not to mention the “free” re-order they offered me. After reading the reviews I am NOW skeptical about using them, because I am not sure if they are Authentic and if they are I am worried about the “bad” ingredients……..

    1. Mine came out the box too, but I’m sure it was to save on shipping.
      The smell is because the herbs used.
      I’ve got mine and it’s 9pm… I haven’t eaten since 12 and no urge to eat.

  10. I have been looking for a supplement for quite a while. However, this does increase my anxiety.

    I did notice when quitting, that a cup of coffee before the gym helps WAY more.

  11. I received my bottle in the mail today. I have not tried the supplement yet, but I have a major concern. My capsules look nothing like the PhenRx capsule on the bottle or the website. My bottle shows a white/blue capsule; however, when I opened the bottle, the capsules are completely clear with revealing the tanish color supplements within it. This is very concerning to me that I possible don’t even have the correct supplement. I googled the PhenRx capsule image to see if any pictures showed the type of capsules that are in my bottle. Online they are all white/blue capsules. I will be emailing the company about this.

    1. I also opened by bottle and got clear capsules. I was very concerned as well because my coworkers also ordered the same product and the capsules were white and blue. I need to email the company also

    2. Will you please let us know if they respond to you, I have yet to start taking mine, but I’m interested in their response.

    3. The clear ones are fake, DO NOT TAKE, you don’t know what you are consuming, very dangerous.

  12. I bought the Phenrx patches on groupon for $20. Its for an entire month, I can honestly say i am extremely happy with the results, I have been taking it for about a month and have lost a pound a day! It has completely changed my body, I dont have side effects, I finally have enough energy to exercise, But i had lost 20 pounds without doing anything, I have no appetite at all, I forget to eat, So i set up alarms throughout the day to at least eat veggies and food throughout, I may have risen my blood pressure but i take meds for that so its not an issue for me, If you are desperatwly trying to lose weight fast this is perfect, I was too overweight before to be able to exercise and had no energy, So now i amslowly trying to do so, I just walk about 15 minutes a day for now, I also learned that doing weights is supposed to be more effective than cardio. People that saw me a month ago are amazed at how i look. The first thing they always ask is how? Well know you know too. Best of luck on your journey.

    1. Hey Roxanne , I have a question hope u can clarify for me. I also order Phen rx patch. I have tried google but nothing on image of patch due to the fact when I recieved it. Inside bag was unfolded phen rx box and packing of patches outside box. so not sure if they are the real thing. Thanks

    2. I ordered mine from groupon as well, and they came this way also. I started yesterday and already notice the energy boost!

    3. I got mine yesterday…where do you put your patch at. It says “naval” area but nothing else.

    4. I received mine monday and started yesterday. Yesterday, I was a little jittery but today I am noticing I have energy and I am not hungry. One question for everyone though, do you keep your patch on while you sleep? I wore mine for 16 hours yesterday. Took it off when I got home and replaced it with new one this morning.

    5. Yes, it smells a bit like Icy Hot but it’s not strong or noticeable once you apply the patch.

  13. I’ve taken many diet pills and this one made me absolutely sick. I could barely function. Bad stomach pains, sick feeling, I can rarley think of a time I was that sick. Unbelievable. Only took 2 pills. This was not for me. I’ve even had the RX prescribe to me and felt nothing like this.

  14. I was surprised to see bad reviews as I’ve had very good results from Phen rx. It gives me that extra push to be able to hit the gym after a 10 shift. I am concerned by the dangerous ingredients list and would like to add that this drug and also the ones you listed are no longer offered on

  15. Ugh, I bought these and felt like an idiot. I felt so jittery and anxious, and when mixed with clinical depression , caused me to be even worse. Nausea alllllll day, and when I was off, appetite came back full force. There were times when I was sure my heart would beat out of my chest. Wouldn’t recommend.

  16. I got my bottle with a piece of paper what offered me a free bottle. I followed the link and apparently when I leave a ( true)review about phen rx and I send them the link of my review, I get a free bottle. Not sure yet if this stuff works, but nowadays everyone wants something for free. So I would like to see real reviews! Since I get hungry from it. But I had to try something since Saba changed their formula.

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