GNC X12 Review

Editor's Review: 3.8 / 5.0

What You Should Know

Click Here To See Our Highest Rated Review

GNC is a supplement company with a long reputation for quality products. The GNC X12 product is designed as a metabolism booster with a thermogenic blend that will help dieters burn calories more efficiently. While thermogenics are a benefit in a weight loss supplement, we will look at the GNC X12 formula more closely to see if it can deliver on its promises.

This product claims to help you burn twelve times more calories than you would burn without a supplement. GNC also promises that their X12 formula will support improved endurance and performance. Unfortunately, the company does not appear to provide any scientific evidence or clinical research to support these claims. The lack of information makes us wonder if this formula really is as good as it says or if the company is luring consumers into purchasing their product based on unsupported claims. We are pleased to find that GNC provides a complete ingredient list for products so customers can decide for themselves if the formula is really as potent as it says.


The GNC website includes a complete listing of product ingredients, which includes Caffeine, Black Pepper Extract, Capsicum Fruit Extract Bioperine, Cellulose, Titanium Dioxide (Natural Mineral Whitener), Gelatin, Artificial Colors (Blue 1, Red 40). The company states that there are no artificial flavors, starch, sodium, wheat, gluten, corn, soy dairy or yeast in the formula. This means that the supplement is appropriate for many consumers, even those with dietary restrictions.

Caffeine is a standard ingredient in thermogenic formulas because it can boost the metabolism and increase energy. However, there are safe and unsafe levels of this substance and too much of a good thing can result in nervousness, jitters, irritability and insomnia. Black pepper extract and capsicum may have some thermogenic properties, but we believe there are more effective products available for this purpose.

Product Features

We are disappointed in the fact that GNC does not appear to offer any sort of money back guarantee on their products. We believe that this policy shows confidence in the product by the manufacturer and offers consumers the chance to try new formulas risk free. The product sells in GNC stores and on the company website for about $25 at the time of this review. This is a significant savings over the original price of almost $50 per bottle.

See Our Featured


  • GNC X14 is a thermogenic that can boost the metabolism and burn calories.
  • The product is currently offered at a discounted price on the company website.


  • The thermogenic ingredients may not be the most effective.
  • There isn’t anything in the formula to act as an appetite suppressant.
  • The company does not appear to offer a money back guarantee.


While we like the ideas of thermogenics in a weight loss supplement, we are not convinced that the substances in GNC X14 are the most potent ones available. We would urge consumers to look for top quality products and ingredients to get the biggest bang from their weight loss buck.

21 User Reviews About GNC X12

Leave comments below
  • 1
    Stephanie h

    So, my first time raking x 12..but not my first time taking a thermogenic. Horrible. So about 25 min into my workout I thought I had to throw up. So I walked outside and then proceeded to sit on the ground because the cramps that camp a few minutes after we’re unbearable. I literally though I was dying. It took about 10 min for the pain to go away. Following hours later came headaches and I couldn’t get cool. I took this pill with a doughnut, of course not a full meal. So apparently if you take with a meal this wouldn’t have happend. Anyways, I’m going to try it again but with food. If this happens agains, I will more than likely return.


  • 2
    Ttacy Ross

    How long does X12 stay in your system once administered?


  • 3
    Trent Forney

    Were could i purchase the x12 fatburns product separately store or website on hand


  • 4
    shalisa walker

    Were can i find x12 at


  • 5

    My boyfriend had me try it out. I misread the directions, and I ended up taking two pills instead of one. It made me really jittery and it made me get sick twice and it felt like my heart was going to beat out of my chest….Does anybody know exactly how much caffeine is actually in x12?


  • 6

    just started taking this and I think its going to be great it gives me extra energy to push through my 3 miles quicker and I am just going to take it on the days I work out so I don’t get too dependent on it, I am not trying to lose weight, just a little baby fat.


  • 7

    im taking lipofuze now but it doesn t seem 2 work … can i take x12 while on other diet pill?


  • 8

    My sister and I took it at the same time. I didn’t have any adverse effects aside from mild stomache cramps…probably from all the pepper.She did get really flushed(red,itchy) but was fine after an hour,she did a little bit the next time,but hasn’t had a problem with it since. It’s actually really common and nothing to worry about,you shouldn’t have a problem after 2 or 3 times. There’s nothing unusual in there,it’s not too strong. It’s not like hydoxycut or xenadrine which zaps your appetite and makes you jittery. It’s more like an aid to your workout. You HAVE to workout to lose weight on this product but it does work if YOU work too. For example,if you run a mile,it’s like you ran 2 or 3. And the good thing about it is when you stop taking it,you won’t gain the weight back like on a strong diet pill.


  • 9

    I wanna know how long would it take for me to lose 20 pounds using this product?


  • 10




    most of them are not. it really is flushing from the niacin. for most of them


  • 11

    I am LOVING this product! It totally helped me blow through my plateau, and I lost 7 pounds in the first week!

    Do not take it on an empty stomach. If you are taking it before breakfast on the non-exercise day, then you definitely need to eat something right after. It gives stomach pains, nausea, etc if you do take it on an empty stomach. Obviously really easy to avoid….just take it with food and water!!

    Reviewers state that this is a mild product, and make it seem like that’s a bad thing, but to me that’s a perk! If you can’t handle a lot of caffeine, then this is a good fat burner for you.

    When exercising, the sweat just drips off and you can totally tell it’s working. Yep, two thumbs up for this one!

    PS. Check the ingredients. Google each one. If you’re allergic to any of them, do not take the product. With any product or food, don’t consume it if you might possibly have an allergic reaction to it.



    I agree I have only been taking it for 2 days and so far I am down 4.5lbs… This pill with exercise is good! And you really don’t have the jitters or shakes. I like it!



    Are you guys taking only one pill? the box recommends one but the lady at GNC told me to start with one the up to two.


  • 12
    Kevin smith

    I had the same allergic reaction, minus the throat swelling. I got red in the face first, than blotches on neck back chest and shoulders. It felt like I had a fever. I immediately to Benadryl, which helped within an hour.


  • 13

    Horrible!!! I took X12 one time and it made me have a severe allergic reaction to it. It made my whole body feel like it was on fire and it made me red and itchy all over, then it closed up my airway (very scary) and it gave me extremely painful cramps in my stomach. I was laying on the floor in the fetal position crying for about an hour before the cramps subsided a little. It made me throw up as well, but even after that, I still felt the after math of it. Please stay away from this product. I have read many other reviews on this and almost everyone has had the same experience as me. Dont so it!



    It’s a side effect called flushing, not an allergic reaction. google it



    Anaphylaxis is rare, but it’s the most serious allergic drug reaction and is a medical emergency. Anaphylaxis symptoms usually start within minutes after exposure to a drug. Drugs you put on your skin can take longer to cause a reaction. Signs and symptoms of anaphylaxis include:

    * Tightening (constriction) of the airways and throat, causing trouble breathing
    * Shock, with a severe drop in blood pressure
    * Weak, rapid pulse
    * Nausea, vomiting or diarrhea
    * Dizziness, lightheadedness or loss of consciousness

    It’s possible to have an allergic response to a drug that caused no problem in the past.

    Yes, this is an allergic reaction and I had one YESTERDAY! I was getting ready to call an ambulance before I passed out from lack of oxygen. My face swelled and I could barely breathe. My stomach was cramping up. I tried to vomit but couldn’t. This is serious. I could have DIED yesterday. This is the scary part…I have been taking this product for over a month off and on. For some reason yesterday, the pill reacted differently with my body. I have reported this to GNC and will report it to the FDA as well.



    It put me in the hospital after two months of taking it, just got up took it ate breakfast and an hour later thought I was dying from a heart attack, maybe a bad batch or something–scary


  • 14

    i tok X12 but it hardly shows ant difference its very light but its very safe


  • 15
    tywonna griffin

    do the x12 wrok i need to loss about 55 pounds


Have a comment or question about GNC X12?