ON Serious Mass

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43 reviews
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ON Serious Mass | High-Calorie Weight Gainer

Optimum Nutrition Serious Mass is the ultimate in weight gain formulas. With 1,250 calories per serving and 50 grams of protein for muscle recovery support, this instantized powder makes the ideal post-workout and between meals shake for sizing up your goals. Serious Mass provides you with the tools you need to pack on the pounds and help you develop the physique you’ve always wanted.


Highlights of Optimum Nutrition Serious Mass:

  • Adding Calories Has Never Been This Easy or Tasted So Good
  • 1,250 Calories
  • 50 Grams of Blended Protein
  • Over 250 Grams of Carbohydrates with NO ADDED SUGAR
  • Creatine, Glutamine and Glutamic Acid
  • 25 Vitamins and Essential Minerals
Customer Reviews
4.8 Based on 43 Reviews
5 ★
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United States


I got this for my husband. It smells great and he said it tastes good. Definitely helps him get in extra calories.

Roberta H.
United States United States

Excellent weight gain

Mixes great and adds to my morning smoothies

Mason A.
United States United States

Great Protein

My experience with Serious Mass has been nothing but great. Constantly pushing my body to the limits requires some serious fuel to rebuild it, & Serious Mass is getting the job done for me.

Caleb B.
United States United States

Mixes well, tastes great, but not very many servings

Great product. I liked the taste and the nutrition facts speak for themselves, but it's tough when it only has 8 servings per container (16 if you split it). But overall I'd still rate 5 stars because it's helping me reach my weight goals.

Mike S.

Overall the taste is good

Overall the taste is good and for the price you get a good size tub of weightgainer. A couple minor gripes is that the scoop size is not like your Typical scoop—it’s like a shovel. Won’t easily fit into most shaker cups which makes For some tricky, awkward mixing. Also the powder is so fine that the slightest sharp movement will result in powder all over yourself! All in all it tastes good; not the best for easy quick mixing but the price is pretty fair for the quantity. Worth trying once

Nutrition Info

Warning Concerning California Residents: This product may contain chemicals known to the State of California to cause cancer and birth defects or reproductive harm.