Serious Mass
Optimum Nutrition

Serious Mass

Protein Powder Weight Gainer*
Loaded with 1,250 Calories, 250g of Carbs, & 25 Vitamins and Minerals to Pack on Pounds*
8.5  out of 10  (1,119 Reviews)
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Product Overview

Two Optimum Nutrition bottles standing next to each other.






High-Calorie WeighT GAiner

  • 1,250 Calories per Serving
  • 50 Grams of Protein per Serving
  • 250+ Grams of Carbohydrates per Serving
  • No Sugar Added
Optimum Nutrition Micronizec creatine power bottle

Optimum nutrition true strength

True Strength is a journey. It never rests, it never quits. It's about overcoming obstacles, accomplishing goals, and recognizing achievements. And then it resets to achieve again. As your trusted sports nutrition partner in goal achievement, ON demonstrates that same passion while crafting our products. From the raw materials we source to our state-of-the-art manufacturing processes, no compromises are made. You set the bar higher after every workout, we set the bar higher to redefine the industry standards and ensure you realize optimum results.


Packing a very substantial 1,250 calories into every serving – even more when mixed with cold milk – Serious Mass is the ultimate weight gain formula. With 50 grams of muscle building protein, when used in conjunction with a healthy, balanced diet and regular weight training, this powdered mix provides you with serious weight gaining support for developing your physique to the fullest.*


Optimum Nutrition has been spotting the efforts of goal driven individuals since 1986. As one of the few companies to operate state-of-the-art manufacturing facilities that are GMP compliant, ON assures that every shake will mix up effortlessly because of its first-to-market instantization process. You also expect each shake to taste the same as the last and your next. That's the kind of consistency ON delivers.

History & Heritage

Optimum Nutrition is legendary for both quality and innovation. In addition to producing the world’s best-selling whey protein, ON’s Gold Standard 100% Casein introduced slow-digesting nighttime protein to the weight training world and Amino Energy created the anytime energy category in sports nutrition. When technology makes advancements possible, ON will be the company bringing it to you.

serious mass ideal usage occasions

Ratings & Reviews

Overall Rating
1,119 Ratings
Verified Buyer Rating
431 Ratings
Average Flavor Rating
7 Flavors
Top Rated Flavor
Chocolate Peanut Butter
By clicking the button above, you agree to entering the Reviews section. Products in the Store are not intended to diagnose, treat, cure, or prevent any disease.
May 08, 2019
Verified Buyer
  • 9 Banana

I ordered this product for after I had my tonsillectomy. With needed rest and the inability to eat solid foods while recovering, I anticipated I might lose weight. I used this product for a good 3 weeks after my surgery and it greatly helped me maintain my weight. I probably only lost about 2-5 pounds total (which is well below what most adults lose after a tonsillectomy) and I didn't notice a significant reduction in muscle, if any. Flavor was great and blended well in a blender. Of course, the texture/flavor was very slightly artificial. I really did enjoy the product though, and continuously looked forward to my smoothies during a difficult recovery. For people just looking to gain mass while still able to eat solid foods as well, this would be a great supplement, too. Would definitely order again!

Apr 30, 2019
Verified Buyer
  • 1 Strawberry

Ive been using this protein for a while, I usually get chocolate, but this time i followed the recommendations of another reviewer and got strawberry.... Terrible, terrible, terrible mistake. It tastes like nasty cough syrup. I drank a serving two hours ago and im still sick to my stomach. Every time I get up I feel like I have to throw up. I've never had this problem with the chocolate flavor, I am 100% going to return this and demand a refund/exchange. Please, please avoid strawberry by all means necessary.

Apr 17, 2019
Verified Buyer
  • 10 Strawberry

I've been using this product for several years now, and I LOVE IT!! don't know how the other flavors taste but, the Strawberry flavor is the BOMB!!! Baby!!

Mar 31, 2019
Verified Buyer
  • 1 Vanilla

Although this Mass Gainer mixes well, the taste is Absolutely horrible. I don't know if I got a bad bag but the powder taste chalky. I've tried with water, with milk, mixed with fruit but no good. I do not recommend this product at all.

Mar 18, 2019
Verified Buyer
  • 10 Vanilla
Mar 17, 2019
Verified Buyer
  • 9 Chocolate

I gained 3-4kg in the first month using this mass even though my body is really hard to gain weight. It is hard to consume the whole 1200 calories serving at once but you can divide it by half and take it separately. Indeed, I found this way is more efficient to me than take the whole serving at once. Btw, the chocolate flavor is pretty delicious for a weight gainer product, it's not too sweet!

Feb 18, 2019
Verified Buyer
  • 9 Chocolate Peanut Butter

I have ordered this while doing Jay Cutler's living large workout and have seen amazing results. I have had tons of trouble gaining weight during workouts when bulking and have seen great results in the last month while drinking 1 serving of this mass gainer a day. Yes it is hard to drink sometimes but the flavor is more than tolerable and the results speak for themselves.

Jan 30, 2019
Verified Buyer
  • 4 Chocolate

Hardest thing to drink ever, is there any way to dim the taste, all I can taste is vitimans and it leaves a sickening feeling .

Jan 23, 2019
Verified Buyer
  • 6 Chocolate

You can’t use it with shaker, only with electric mixer. You can’t dissolve in water using your protein shaker.

Jan 22, 2019
Verified Buyer
  • 10 Chocolate

This is the best tasting powder I’ve ever had! I’m almost done with my first 12 lb bag and another is on its way. I’m a Monday through Friday lifter and those are the only days I take this. I’m one of the few looking to gain weight and not lose it. I started this bag at 198 lbs and three quarters of the way though it I’m up to 209. I have a personal goal to get to 225 lbs and I don’t think it’ll be a problem with this powder.

Jan 07, 2019
Verified Buyer
  • 10 Chocolate

This is the second time I ordered 12lb serious mass, it is easily dissolved in water and it tastes great. I used it three times a day, each time 1/2 scoop, and I gained 8-9kg in less than 2 months. I suggest it to anyone who wants to get weight.

Jan 06, 2019
Verified Buyer
  • 4 Chocolate Mint
Dec 30, 2018
  • 8 Chocolate

Tastes great but (and its a big one) The protein types in this product are inferior ! No protein isolates and no micellar casein which is poor.. i would opt for the signature mass gainer which has much better formula!

Dec 05, 2018
Verified Buyer
  • 4 Strawberry

takes a while to mix, and straw berry has kind of a medicine/vitamin taste to it

Nov 30, 2018
Verified Buyer
  • 10 Chocolate

Amazing weight gainer for someone who has difficulties putting on serious mass aswell as lack in vitamins. This product tastes great and does wonders. Consistency is very light for someone who isnt used to this type of intake, would highly recommend if youre looking into putting on some serious weight mass/muscle.

2 Sizes
12 Lbs.
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6 Flavors
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Price: $55.18  ($3.45 / Serving)
Flavor Rating: 8.4

What's in Optimum Nutrition Serious Mass

12 Lbs. Chocolate
Supplement Facts
Serving Size2 HeapingScoops(334g)
Servings Per Container16
Amount Per Serving In Water % Daily Value
Calories 1250
Calories From Fat 40
Total Fat 4.5g 7%*
Saturated Fat 1.5g 8%*
Cholesterol 80mg 27%
Total Carbohydrate 252g 84%*
Dietary Fiber 4g 16%*
Sugars 20g
Protein 50g 100%*
Vitamin A 5000IU 100%
Vitamin C 60mg 100%
Vitamin D 200IU 50%
Vitamin E 30IU 100%
Thiamin 4.8mg 320%
Riboflavin 4mg 235%
Niacin 50mg 250%
Vitamin B6 5mg 250%
Folic Acid 400mcg 100%
Vitamin B12 10mcg 167%
Biotin 300mcg 100%
Pantothenic Acid 25mg 250%
Calcium 590mg 59%
Iron 8mg 44%
Phosphorus 430mg 43%
Iodine 150mcg 100%
Magnesium 140mg 35%
Zinc 15mg 100%
Selenium 70mcg 100%
Copper 1.6mg 80%
Manganese 2mg 100%
Chromium 120mcg 100%
Molybdenum 75mcg 100%
Sodium 410mg 17%
Potassium 1560mg 45%
Creatine Monohydrate 1g
L-Glutamine 500mg
Glutamine Peptides 500mg
Choline (As Choline Bitartrate) 250mg
Inositol 250mg
PABA (Para-Aminobenzoic Acid) 5mg
* Percent Daily Values are based on a 2,000 calorie diet
† Daily Value not established
Other Ingredients:
Maltodextrin, Protein Blend (Whey Protein Concentrate, Calcium Caseinate, Egg Albumin, Sweet Dairy Whey), Cocoa (Processed With Alkali), Natural And Artificial Flavor, Vitamin And Mineral Blend (DiPotassium Phosphate, Magnesium Aspartate, DiCalcium Phosphate, Calcium Citrate, Ascorbic Acid, Niacinamide, Zinc Citrate, Beta Carotene, D-Calcium Pantothenate, D-Alpha Tocopheryl Succinate, Selenomethionine, Copper Gluconate, Ferrous Fumarate, Manganese Amino Acid Chelate, Thiamin Mononitrate, Pyridoxine Hydrochloride, Riboflavin, Chromium Polynicotinate, Folic Acid, Biotin, Molybdenum Amino Acid Chelate, Cholecalciferol, Potassium Iodide, Cyanocobalamin), Acesulfame Potassium, Lecithin, Medium Chain Triglycerides.
Allergen Information: Contains Milk, Egg, Wheat (Glutamine Peptides) And Soy (Lecithin) Ingredients.

Directions For Serious Mass:

Add two heaping scoops of Serious Mass to a blender filled with 24 oz (710 mL) of water. Blend for 45-60 seconds. Then add a few ice cubes and, if desired, other calorie-contributing ingredients and blend for an additional 30-45 seconds.

Tips: Mixing two scoops of Serious Mass with 24 oz (710 mL) of nonfat or low fat milk instead of water will give you a thicker, creamier, higher-calorie shake. New users may find if beneficial to begin with 1/2 of a serving daily for the first week and then gradually increase to 1 or more full servings several times a day.

Serious Mass is a substantial weight-gain supplement that can be used to feed serious calorie needs in a variety of different ways.

Between Meals: Drink 1/2-1 serving of Serious Mass between meals to maintain positive nitrogen balance and support a high-calorie diet. Post-Workout: Begin drinking 1/2-1 serving of Serious Mass 30-45 minutes following exercise to support maximum recovery. Before Bed: Drink 1/2-1 serving of Serious Mass about 45-60 minutes before bed to provide nutrients to recovering muscle throughout the night.

Note: For best results use Serious Mass combined with intense weight training (3-5 times per week) and a sensible whole foods diet. Also, keep in mind that sufficient recovery between workouts impacts your ability to gain lean mass. Allowing at least 48 hours between workouts involving the same body parts is recommended.

Warnings: Keep out of reach of children. Do not take this product if you are pregnant or nursing a baby. Check with a qualified healthcare professional before using this product if you are under 18 years of age or if you have any known or suspected medical condition(s) including diabetes, hypoglycemia, and/or if you are taking any prescription or OTC medication(s).

* These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
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