Optimum Nutrition Serious Mass 12lb

88% of 100
Save $15.00
$5.62 per serving
Buy now, Pay later
In Stock
Free Delivery
Need some help? Just Ask
This product is available in-store - use our store locator

Optimum Nutrition Serious Mass is the ultimate muscle building and weight gain formula. Each serving supplies 1250 calories including 250 grams of carbohydrates, 50 grams of protein, and 3 grams of creatine monohydrate, in addition to 25 vitamins and essential minerals, to increase nutritional intake and support your size-related goals. When used as a complement to a balanced diet and optimal training routine, Optimum Nutrition Serious Mass can assist you in maintaining a positive caloric balance and enhance your ability to put on quality muscle mass.



  • Easily consumed high calorie formula to support muscle building and weight gain goals
  • 250-plus grams of carbohydrates per serving
  • 50 grams of protein per serving
  • Enhanced with creatine monohydrate and glutamine for muscle growth and recovery
  • 25 vitamins and essential minerals

Optimum Nutrition Serious Mass can be used post-workout and/or between meals as a complement to a balanced diet. Mix 2 scoops with either milk or water, and blend with additional ingredients such as fruit or peanut butter if desired. When new to using Optimum Nutrition Serious Mass, start by consuming a 1 scoop half-serving.

Nutritional Information for Chocolate Flavour

Optimum Nutrition Serious Mass review by maor1k1d
  • Flavour
  • Formula
  • Effectiveness

I used this in conjunction with a high calorie diet while I was trying to pack on some quality size. Being a hard gainer, even eating a tonne of food didn't do too much for me. So with O.N. Serious Mass I was blown away by the quality of the calories. Most weight gainers i've tried previously have an extremely sugary taste, or have an odd paste taste. O.N. was leaning more towards the paste side, but still I was able to enjoy the flavour. It might just be that I don't like to use too much liquid, i'd rather a smaller, thicker drink, than a smooth, but twice as much gainer. Along with the extra calories I was trying to consume with my high activity job at the time, it just made for easy calories when it wasn't viable to sit down for 30 min and eat a protein/carbs/fats meal. I'd definitely recommend this to anybody trying to put some size on without having to drink pure sugar for 20 minutes.

Optimum Nutrition Serious Mass review by Aprilia
  • Overall
  • Flavour
  • Formula
  • Effectiveness

I have tried the ON Serious Mass chocolate and vanilla flavours. The vanilla is by far the best. It mixes reasonable easily and the vanilla is a great flavour to blend with fresh fruit. The formula has a comprehensive list of supplements added - vitamins, amino acids and minerals. By far the most comprehensive of any mass gainer. I have tried this as well as Mutant Mass (still have half a bag of MM left - terrible taste). You will gain weight on this product. I use it as a meal replacement by blending with fresh fruit, yoghurt, yakult, non-fat milk and coconut water. Like the effect of a lot of these supplements, you might get diarrhea.