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FREE Shaker with 100% Gold Standard Whey purchase

When you buy a 908g or 2.27kg tub

Serious Mass

  • Supports muscle building and weight gaining
  • More than 1260 kcal per serving to help boost your calorie intake
  • 50 g protein per serving to help build and maintain muscle

Product Overview


Do you want to gain weight to improve your sports performance? It can be difficult to achieve this with only food and diet. This is certainly true for people with a high metabolism. As well as people with a busy lifestyle and those who do not feel hungry a lot. That’s where Serious Mass can definitely help you. It helps you take in more calories and successfully gain weight with its ultimate weight gain formula. Every serving contains more calories (1,250g) to increase how much you take in each day. It is high in protein (50g) which is good for your muscle growth and repair. The level of carbohydrates (250g) also help you with muscle recovery after training. As an extra bonus, it now includes Creatine (3g) that naturally helps your muscles to produce more energy during exercise. More energy helps you with endurance sports, such as cycling, swimming and running. The extra muscle it helps to build will also help people serious about weight gain to achieve their goals.


Ready to mix powder that already contains protein, carbohydrates, vitamins, minerals, and sweetener.


  • Ideal for people who want to gain weight

  • Increase your daily calorie intake to achieve your goal

  • High level of proteins (50g) to repair and grow muscle

  • Carbohydrates(250g) to help recover muscles after training

  • Gives you more energy for endurance sports with Creatine (3g)

Suggested Use

For best results, we recommend that you take your shake between meals when you need extra calories. You can also have it after your workout, which will support your recovery.

Mix 2 heaped scoops with 710 ml of water.

Nutritional Information

Nutritional information will be shown when a flavour and/or size is selected.

Customer Reviews

Overall Rating (4.6)
Write your review here. For complaints and questions we would like to refer you to our customer service.
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Best Shake EVER!!!!!!

Review by Jane557 on May 20, 2022
Not sure why people don’t like the vanilla I love it!!! Just now as excited to try the other flavours of vanilla is said to be the worst ha! I absolutely love this shake and how much calories I can get from just one drink!! I struggle to gain weight (appetite and fast metabolism issues) and this is THE best I have ever tried. I love how it does not have all of that nonsense thickening agents (guar gum, xanthan gum, etc) that makes protein shakes taste terrible! I hate the slippery and heavy texture it gives so I am absolutely thrilled that I found this one that has none of those nasty ingredients! Please don’t ever change the formulation it’s perfect!!

Great Weight Gainer

Review by Anonymous on Apr 20, 2022
bought it for my son who is starting training for Army and he says he can feel the difference

Really helpful

Review by Anonymous on Apr 5, 2022
This is the only gainer which helped me to gain weight. I tried Gnc gainer but it didn't even helped me to gain 1kg of weight and it was excessively sweet which always made me feel uncomfortable and sick. I didn't have any hope from this but I just tried it and was shocked from the results. I started it with 1 scoop per day for a week and then increased it to 2 per day. I gained 7kg of weight in just 1.5 months . The flavour I bought was vanilla, it was not much sweet , nothing bothered me at all. I just enjoyed drinking it with adding a banana and one spoon of peanut butter and drinking it in my breakfast and in the evening. My diet was not much, but still i managed to gain . The only cons I feel is that at the time using it, I started having lot of acnes on my face , but I don't blame this supplement because I didn't use to drink even one glass of water those days. Also it lasts only 1 month or max 1.5 month. I never gave a review earlier to a product but I am so happy with the results that it convinced me to give a review. Definitely going for another one.


Review by Anonymous on Mar 10, 2022
Very tasty flavour

Excellent protein!

Review by Anonymous on Mar 5, 2022
I love this product so much! I started using it for a while now and I’ve been seeing results! Works great!

Good for building mass

Review by Anonymous on Mar 2, 2022
It's good for any beginner and intermediate to build a mass. The taste is awesome.

Great product, super slow shipping.

Review by Anonymous on Mar 1, 2022
Product is one of the best. Order a week or more early, the shipping is terrible.


Review by Anonymous on Feb 28, 2022
Great quality,first time ordering directly from Optimum Nutrition.No problems.

No scoop

Review by Fintan Carroll on Feb 12, 2022
I haven’t got a scoop with my tub and was wondering how many tablespoons would be equal to one scoop Great product cannula is very nice

Serious Mass

Review by Anonymous on Feb 4, 2022
I order this product to help my son gain muscle mass. He enjoys the taste and it mixes well using a blender. Quick delivery and great customer service

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