Optimum Nutrition Serious Mass Review

Many of us struggle in gaining weight. And if you are one of those many, know that a high-calorie diet is a must to help improve your body mass. Your caloric intake must be higher than the calories you are burning. 

One way to increase your calorie consumption is to eat way more than you are used to. 

However, this can be a little too overwhelming if you tend to have a weak appetite, if you are a serious hard gainer that needs to maintain high amounts of calories daily or if you are having a hard time including a meal in your busy schedule. 

Here is where weight gain shakes come in, it is a revolutionary product that helps in solving those problems for you. 

Weight gain shakes are a supplement that is added to your diet to help increase your body weight as it is packed with a high amount of calories, proteins, and everything you need in a very convenient way. 

Serious Mass by Optimum Nutrition is one of the best high-calorie weight gainer shakes available in the market. 

Optimum Nutrition, Inc. has been known to set the Gold Standard when it comes to sports nutrition, helping focused athletes achieve their goals for more than 30 years.

Combining it with muscle-building exercise will definitely allow you to gain muscle mass and achieve the physique you’ve always wanted. 

Interested to know more? Keep reading as we provide you with an in-depth review of Optimum Nutrition Serious Mass. 

We’ve included its pros, cons, and features to help you decide if this can help you achieve your fitness goal. We’ve also collected some reviews from various online platforms.

Without further ado, let’s start! 

TLDR: Optimum Nutrition Serious Mass Weight Gainer Overview

Optimum Nutrition Serious Mass Weight Gainer

Intended to boost caloric intake, Optimum Nutrition Serious Mass Gainer is packed with 1,250 calories, 254 grams of carbohydrates, and 50 grams of blended protein per 2 scoop serving. 

Making it a great option for those looking for some serious bulk up, gain weight, and for those who would like to meet their caloric requirements. 

Aside from a high amount of macros, it also contains 25 vitamins and essential minerals including 3 g creatine, 500 mg glutamine, and glutamic acid to help you keep going in your workout and muscle recovery. 

With a variety of flavors to choose from, you can customize how you like them by adding frozen fruits, nuts, or peanut butter to further increase calories and improve the taste.

Serious mass protein uses a blend of whey protein concentrate, calcium caseinate, egg albumen, and sweet dairy whey. On a side note, you may need to take extra precautions if you are allergic to eggs, milk, and soy.

Together with your workout program, optimum nutrition’s serious mass is best taken as post-workout, in between meals, or before bed to keep those pounds coming.

[You might also want to read: MRM Massive Muscle Gainer Review

Best For:

  • Manufactured by one of the most trusted brands when it comes to nutritional supplements
  • With various flavors to choose from
  • Banned substance tested
  • Taste great
  • New look, same trusted quality
  • A convenient way to increase your calories, macros, vitamins, and minerals
  • Does a great job in providing high calories per serving

  • Like other dietary supplements, this has not been evaluated by food and drug administration
  • Contains allergens: egg, milk, soy
  • You may need to use a blender to mix the product well; some find it a hassle to do as you need to clean it every time
  • It has less serving per container compared to other competitor brands
  • They do not offer money-back guarantee or warranties 

Interested? Here’s the link to purchase it! 

In-Depth Review: Optimum Nutrition Serious Mass


The Optimum Nutrition Serious Mass comes in a 6.07 x 11.18 x 18.32 inches packaging for a 12 lb pack and 7.83 x 7.87 x 10.27 inches packaging for a 6-pound pack.


Maltodextrin, Protein Blend (Whey Protein Concentrate, Calcium Caseinate, Egg Albumen, Sweet Dairy Whey), Cocoa (Processed with Alkali), Natural and Artificial Flavors, 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), Lecithin, Acesulfame Potassium, Medium Chain Triglycerides.

Serious Mass Nutrition Facts

Serving Size: About 2 Heaping Scoops (226 grams)

*Percent Daily Values are based on 2,000 calorie diet

Amount Per Serving % Daily Value
Total Fat4.5 g6%
  Saturated Fat2.5 g13%
Cholesterol110 mg37%
Total Carbohydrates 252 g92%
  Dietary Fiber4 g14%
  Total Sugars 20 g**
  Includes 9g Added Sugars18%
Protein50 g100%
Vitamin A (Beta-carotene)750 mcg83%
Vitamin C (Ascorbic Acid)60 mg67%
Vitamin D (Cholecalciferol)5 mcg25%
Vitamin E (D-alpha tocopherol Succinate)20 mg133%
Thiamin (Thiamin mononitrate)4.8 mg400%
Riboflavin4 mg308%
Niacin (niacinamide)50 mg313%
Vitamin B6 (pyridoxine hydrochloride)5 mg294%
Folate (Folic acid)680 mcg DFE (400 mcg folic acid)170%
Vitamin B12 (cyanocobalamin)10 mcg417%
Biotin (d-biotin)300 mcg1000%
Pantothenic Acid (d-calcium pantothenate)25 mg500%
Choline (choline bitartrate)250 mg45%
Calcium (calcium citrate, dicalcium phosphate)600 mg46%
Iron (ferrous fumarate)8 mg44%
Phosphorus (dicalcium phosphate, dipotassium phosphate)590 mg47%
Iodine (potassium iodide)53 mcg35%
Magnesium (magnesium aspartate)140 mg33%
Zinc (zinc citrate)15 mg136%
Selenium (selenomethionine)70 mcg127%
Copper (copper gluconate)1 mg111%
Manganese (Manganese Amino acid chelate)2 mg87%
Chromium (chromium polynicotinate)120 mcg343%
Molybdenum (molybdenum amino acid chelate)75 mcg167%
Sodium570 mg25%
Potassium (dipotassium phosphate)1430 mg30%
Creatine Monohydrate3 g**
L- Glutamine500 mg**
Inositol250 mg**
PABA (Para-aminobenzoic acid)5 mg**

Who is it best for?

If you are one of those individuals who are a hard gainer, having a hard time gaining weight, weak appetite, or for people who have a busy schedule to include a mealtime for themselves, then Optimum Nutrition Serious Mass is a good option for you. 

How to Use

For new users, it is best to start with ½ serving every day for a week then gradually increase the amount to 1 or more servings multiple times a day.

For adept consumers, add 2 full scoops of serious mass in a blender and mix with 24 fl oz of your choice of liquid, ideally milk or cold water. You may add ice or any other ingredients you prefer. Blend at a high speed for 45-60 seconds or until mixed well. Once the packaging is opened, store it in a cool dry place. 

Optimal Time to Consume

Depending on what you find most convenient, Optimum Nutrition Serious mass can be best consumed: 

1. In the morning – starting your day with a high-calorie meal can help you feel more energized and fueled all throughout the day. This can also be advantageous for those who are running late and don’t have much time to cook and prepare for their breakfast. 

2. After a workout or intense training – Your body’s glycogen level decreases after a workout, so consuming adequate carbs is important to help replenish your glycogen storage. While protein is needed to give your body the amino acids it needs to help support muscle repair and recovery. This makes mass gainers a great post-workout meal.

3. Before Bed – taking a Serious mass gainer before bed helps ensure that your body has adequate protein to help your muscles recover from the workout while you sleep. However, remember to keep at least 1-2 hours between your last meal and sleep.  

Flavor and Consistency

The Optimum Nutrition Serious Mass comes in 6 flavors: chocolate, strawberry, banana, vanilla, cookies and cream, and chocolate peanut butter. 

People who are a fan of this product rave about how good its flavors are. Consistency-wise, it comes quite close to a milkshake (thick) especially when it is mixed with other ingredients.

It may take a while to dissolve it so it is best to use a blender rather than a shaker.

Value for Money

Compared to other mass gainers available in the market, Optimum Nutrition Serious Mass is pricier than average, this is because they offer a much lesser serving size per container. 

You’ll only be getting around 8 servings in a 6 lb container while 16 servings for 12 lbs, this could be pretty expensive if you are a hard gainer who takes a full serving each time.

However, looking at its nutritional profile as well as being manufactured from a reputable and trusted company, we think that Optimum Nutrition Serious Mass Gainer is worth it and provides an excellent value for money.

Possible Side Effects

People with allergies may have to be extra careful before getting this product as it contains common allergens such as eggs, soy, dairy, and wheat. Diabetics and hypoglycemics also need to check in with their physician as this contains maltodextrin, a type of sweetener that can spike up their blood sugar. 

Bloating and stomach upset are also common side effects. This product could make you feel lethargic and lose appetite due to the density of the ingredients this product gives per serving if not used properly. 

As mentioned above, Best to start with a ½ scoop then gradually increase the serving size.

What Do People Say About It?


The Optimum Nutrition Serious Mass has a good rating on Amazon, Here’s what some of their customers have to say about it: “Firstly, if you are looking for a protein powder that will help you gain LEAN mass, then stop reading right now and look elsewhere. This protein powder is for people like myself who have trouble gaining weight and want to put on some muscle/mass. You also need to make sure you are actually working out, if not you’ll just gain fat. This stuff is a miracle for skinny guys like me, I’ve gained 5 -10 lbs in the last few months and that’s A LOT for me and has never happened before.”

Another wrote: “I went from 160 to 180 from just the 6lb tub. I have been trying different shakes all my life and none of them have given me the results I wanted. This one however gave me results really quickly. Definitely use this to add calories to your meals. Please make sure you work out during the day because if you don’t you will just become fat. I have had many protein shakes before and they ALL have tasted horrible but this one tastes just like chocolate milk. For those saying it doesn’t blend well, you have to either split your servings and/use a blender. I split my servings and I shake for about 3-5 minutes and that gets rid of the clumps. One scoop is huge so naturally, it’s going to be hard to blend but you have to keep shaking. Once it’s blended it tastes like a smooth glass of chocolate milk.”


In this channel, the ON Serious Mass was graded C minus by the reviewers. According to Troy Adashin, a bodybuilder, he’s a pretty tough grader and would have given D or even an F to some other mass gainers because of the flat-out junk and filler in it. But the ON Serious Mass has a little bit cleaner formula, thus, the grade. He also shared some pros and cons of the product. 

On Mitchelle Adagala’s youtube channel, she shares her personal experiences about using the ON Serious Mass and shares some tips and her views on whether it’s worth it or not. Would she recommend it? 

Her answer: “Yes, I would. Especially if you are an ectomorph body type and you’re really struggling with your fast metabolism and gaining muscle mass and gaining weight… If you are really a hard gainer, you are struggling, you are an ectomorph, you’re consuming fewer calories or just plain busy, or when you don’t have time to eat…”

Overall she gives this product an 8.5 out of 10, she thinks that: “Overall it’s really really amazing, you will gain weight on it given that you get to introduce calorie surplus gradually to your body.” 


On the famous online forum Reddit, one user would like to hear what others thought about taking Optimum Nutrition Serious Mass Gainer. He is considering trying it because he is struggling to gain a lot of weight and get that calorie surplus. 

While most comments emphasize consuming more food instead, one shared: “This might be an unpopular opinion but it really helped me get a springboard into eating more. I bought a huge bag when I was in college and would drink it every time I worked out. I went from 110 to 125 and gained a bigger appetite for food. I did gain a little bit more fat than I wanted but it’s fine because I was naturally really skinny.

If you buy it just don’t drink it too often or consecutive days. It can be used on days that you feel like you need a boost in calories.” 

The Verdict: Should You Buy it?

Yes, for hard gainers
Optimum Nutrition Serious Mass Weight Gainer

Consuming real foods is still the best way to help fill in your caloric needs, but if you’re really struggling to gain weight or you’re a hard gainer and feel like consuming too much food is not feasible, then you might want to consider taking Serious Mass by Optimum Nutrition. 

Serious Mass by Optimum Nutrition contains high amounts of calories, protein, and carbs as well as vitamins and minerals that have proven their effectiveness in helping gain weight and muscle build-up, together with a proper exercise regimen. 

However, it is important to take note that this supplement is not a meal replacement. It is called a supplement because it is an addition to your regular diet to help you gain results faster.

Furthermore, you may need to take note of its possible side effects such as bloating, upset stomach, diarrhea, etc. 

As with all supplements, best to consult your doctor or your dietitian first before using this product or when you plan on taking up a new type of diet.

If you like this article, make sure to check out our other articles at ExpertFitness.org

Safety Information

This product is intended for healthy adults over 18 years old together with a healthy balanced diet and exercise program. 

If you are nursing, pregnant, or with a medical condition, you should consult your health care practitioner prior to using this product. 

**Statements regarding dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease or health condition.

Nathan Lloyd, MSc

I’m a personal trainer, based in Boulder, Colorado.
I service clients physically in the Boulder area, mainly in the ONE Boulder Fitness Gym, but am also available for online consulting and coaching.

If you’re interested in my personal coaching programs, please contact me via the contact page.