Optimum Nutrition Serious Mass - 2.73kg / Banana

Optimum Nutrition Serious Mass

2.73kg / Banana
£46.99
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Optimum Nutrition Serious Mass - 2.73kg / Banana
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Optimum Nutrition Serious Mass

£46.99
Free Delivery When You Spend £100
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FOR SAME DAY DISPATCH
  • Achieve a calorie surplus fast with 1,250 calories per serving to support size and mass goals.
  • Build and maintain muscle with 50 g of high-quality blended protein in every shake.
  • Power intense training and recovery with 250 g of energy-rich carbohydrates.
  • No added sugar and great-tasting flavours that mix smoothly for easy daily use.
  • Versatile mass support—use between meals, post-workout, or before bed to keep calories consistent.

Optimum Nutrition Serious Mass – High-Calorie Mass Gainer for Hard Gainers

Struggling to put on size? Optimum Nutrition Serious Mass makes hitting your daily calorie target simple, delicious, and repeatable. If you’re a hard-gainer, a busy athlete, or anyone who needs extra calories without spending hours in the kitchen, this high-calorie mass gainer delivers the nutrition you need to grow—consistently.

Serious fuel for serious results

Each shake packs an impressive 1,250 calories with 50 g of blended protein to support muscle building, plus 250 g of carbohydrates to replenish energy and keep you training hard. And with no added sugar, you’re getting serious calories from purposeful nutrition, not empty sweetness.

Why athletes choose Serious Mass

  • Made for hard-gainers: Easily hit a daily surplus without force-feeding meals.
  • Balanced macros: Protein supports muscle growth while carbs restore glycogen after tough sessions.
  • Convenient and consistent: A reliable shake you can take at home, at work, or after the gym.
  • Trusted quality: From Optimum Nutrition—trusted by athletes worldwide for performance-focused formulas.
  • Mix it your way: Blend with water or milk; add oats, nut butter, or fruit to tailor your calories.

Who is it for?

Hard-gainers, bulking athletes, and anyone with a fast metabolism who finds it tough to eat enough to grow. Serious Mass is ideal between meals, post-workout, or before bed to keep your calorie intake on track.

How to get the most from Serious Mass

  • Start smart: New to mass gainers? Begin with half a serving and build up as your body adapts.
  • Split your serving: Enjoy one half after training and the other half between meals for steady intake.
  • Customise the shake: Milk for extra calories and creaminess; add oats or banana for a bigger boost.

Nutritional highlights

  • 1,250 calories per serving
  • 50 g protein to support muscle growth
  • 250 g carbohydrates to fuel performance and recovery
  • No added sugar

If you’re serious about size, get Serious Mass. It’s the easy, great-tasting way to stay in a calorie surplus and keep your progress moving forward.

Expiry

2.73kg / Chocolate 30-04-2028
2.73kg / Cookies & Cream 30-06-2028
2.73kg / Strawberry 30-04-2028
5.45kg / Banana 30-04-2028
5.45kg / Chocolate 30-04-2028
5.45kg / Cookies & Cream 30-06-2028
5.45kg / Strawberry 30-04-2028
5.45kg / Vanilla 30-04-2028

Barcodes

2.73kg / Banana 5060245600552
2.73kg / Chocolate 5060469985206
2.73kg / Cookies & Cream 5060469983257
2.73kg / Strawberry 5060469988368
2.73kg / Vanilla 5060469985213
5.45kg / Banana 5060245601061
5.45kg / Chocolate 5060245600446
5.45kg / Chocolate Mint 5060469985329
5.45kg / Cookies & Cream 5060469983363
5.45kg / Strawberry 5060245600934
5.45kg / Vanilla 5060245601023
  • 5 stars: 24 (83%)
  • 4 stars: 4 (14%)
  • 3 stars: 1 (3%)
  • 2 stars: 0 (0%)
  • 1 star: 0 (0%)
A
Alec Spicer
Exactly as expected. Huge weigh gain in little time.

I'm a skinny guy who's always fluctuated around 58-60kg.

After 4 days of use I am already at 62.3kg.

Some advice with this product is to not use a full serving. It's way too much for someone small trying to gain weight. Instead you should do a half serving (1 scoop and 300ml of milk) twice a day. This stops you getting the stomach problems that others have mentioned.

It doesn't mix very well. You need a strong blender or a tornado shaker. Manual shaking just ends up with a huge clump of mushy powder.

Taste is okay. I went for chocolate peanut butter and it's not exactly tasty, but it's not bad either. I usually drink it quickly so taste isn't a big thing for me, as long as it's not revolting or super synthetic.

A
Alec Spicer
Exactly as expected. Huge weigh gain in little time.

I'm a skinny guy who's always fluctuated around 58-60kg.

After 4 days of use I am already at 62.3kg.

Some advice with this product is to not use a full serving. It's way too much for someone small trying to gain weight. Instead you should do a half serving (1 scoop and 300ml of milk) twice a day. This stops you getting the stomach problems that others have mentioned.

It doesn't mix very well. You need a strong blender or a tornado shaker. Manual shaking just ends up with a huge clump of mushy powder.

Taste is okay. I went for chocolate peanut butter and it's not exactly tasty, but it's not bad either. I usually drink it quickly so taste isn't a big thing for me, as long as it's not revolting or super synthetic.

V
Victor
Best protein in the market!

I have been using this protein for a long time now and its in my opinion one of the bests. I like the vanilla flavour which if you combine it with milk you barely notice is a protein shake, compared with other brands which can taste awful. I then add some strawberries and mix it together and it tastes even better than a strawberry milkshake from starbucks. Definitely recommend it after or before the gym and will get the calories going for a good bulk.

The only downside is it has many carbs but that's not any different with other protein brands.

T
Toni Pinto
Was recommended

Was recommended this by a friend so I'll give it 5 star and update once a few weeks have past . I have lost 2 stone due to an illness and he recommended this product to get extra calories for weight gain . Used this himself to gain weight and I've seen the difference in him within 2 months . I'll mix with milk not water to bump the calroie intake up. Praying for the same results

M
Muhammad Umer Khalil
Mass gain

My friend recommend this protein to me. I used it for continuously after gym. And saw positive results. Definitely buy it again. Very good for mass gain.

A
A
Great for hard gainers

This product is great. Exactly what you would expect in a weight gainer; high calories, high carbs, quite high in protein. It is perfect for people trying to gain weight, who have a hard time struggling to get those extra calories from solid food. If you are a hard gainer this is a must. I gave this 4 stars, and not 5 for two reasons. First the taste is ok, but since you have to drink so much of it one go, it will kinda make you feel a little sick, and the after taste is not that nice either. Second if you are thinking about taking this in between meals think again. Lets say you take this after breakfast as a snack. Unless you have a super fast metabolism then you would have to wait a lonnng time till you are hungry enough to have lunch, which if you are a hard gainer is not a good thing. Even after a hard workout, where I was obviously hungry I still could not eat for at least 2 hours after taking this. So If you are thinking of taking this only once a day I would suggest taking it right before bed on your rest days, and once straight after your workout on your lifting days(which you should be doing if you a hard gainer). You should always eat solid food, before turning to supplements and if you skip lunch or dinner after taking this then it would be a meal replacement rather than a supplement.

J
Justpoo
Effective product for underweight people

I've always been slim/athletic but after a serious illness I went under nine stone and stayed there (I'm five foot ten). I have a fast metabolism and eating the required amount of food to healthily gain weight was extremely difficult to sustain. I tried eating junky high calorie snacks but realised it was a stupid way of trying to gain weight.

So after buying this product I went straight in and tried to drink a full serving - mistake! I managed it but felt quite ill afterwards. I highly recommend you start with half or even a quarter serving to begin with, just until your stomach adapts. It's now two weeks later and with trial and error I've found that splitting a full serving into three is best for me. One in the morning, one after lunch, one in the evening. I use full fat milk, ice cream and a banana to boost the calories per full serving to over 2000, and I find a blender works great to give a nice semi-thick smooth shake.

When I started a fortnight ago I weighed 8 stone 12, I now weight 9 stone 8, so I've gained roughly 10 pounds in two weeks, with fluctuations along the way. I've just bought another 5.4kg bag and plan to continue to steadily gain until I reach around 11 stone. I bought some weights and with some advice I've started a light exercise programme with the aim of turning the energy to muscle and shaping my body a bit. I have more modest aims than many who take this supplement, I'm not looking to build huge muscles and train super hard, but if you're like me - underweight and a bit unfit - then I recommend this product along with some sort of exercise programme so it doesn't just go straight to your belly. It really does promote weight gain, I've been very pleasantly surprised with the results, and will continue to use the product as needed in order to achieve and maintain my target weight.

The chocolate flavour is very pleasant, if a little sweet, and I now have no problem ingesting what I need to in order to gain weight. It may seem expensive, but at £2.50 a day it works out an easy, reliable and cost effective way to supplement your diet without resorting to less healthy alternatives. It works for skinny old me, and I don't see any reason why it shouldn't work for skinny old you! :)

Edit - it's now 22 days after I first used the product and I'm now just over ten stone, so that's 16lb in 22 days. People are commenting on the difference and it's done wonders for my energy levels and appetite. So all in all I can't recommend this product any more highly, it genuinely works. Can't say fairer than that!

Last update - I'm now at my target weight of 11st, it's taken 54 days for me to put on 30lbs - two stone two pounds in just under two months. That's beyond what I expected. If I could give a final note it would be to watch your body fat as without exercise this product will raise it quite easily. I'm now going to reduce my servings to maintain this weight, with my new increased appetite it's possible that I soon won't need a supplement at all. So that's me signing off, a bit heavier and a lot happier!

J
Justpoo
Effective product for underweight people

I've always been slim/athletic but after a serious illness I went under nine stone and stayed there (I'm five foot ten). I have a fast metabolism and eating the required amount of food to healthily gain weight was extremely difficult to sustain. I tried eating junky high calorie snacks but realised it was a stupid way of trying to gain weight.

So after buying this product I went straight in and tried to drink a full serving - mistake! I managed it but felt quite ill afterwards. I highly recommend you start with half or even a quarter serving to begin with, just until your stomach adapts. It's now two weeks later and with trial and error I've found that splitting a full serving into three is best for me. One in the morning, one after lunch, one in the evening. I use full fat milk, ice cream and a banana to boost the calories per full serving to over 2000, and I find a blender works great to give a nice semi-thick smooth shake.

When I started a fortnight ago I weighed 8 stone 12, I now weight 9 stone 8, so I've gained roughly 10 pounds in two weeks, with fluctuations along the way. I've just bought another 5.4kg bag and plan to continue to steadily gain until I reach around 11 stone. I bought some weights and with some advice I've started a light exercise programme with the aim of turning the energy to muscle and shaping my body a bit. I have more modest aims than many who take this supplement, I'm not looking to build huge muscles and train super hard, but if you're like me - underweight and a bit unfit - then I recommend this product along with some sort of exercise programme so it doesn't just go straight to your belly. It really does promote weight gain, I've been very pleasantly surprised with the results, and will continue to use the product as needed in order to achieve and maintain my target weight.

The chocolate flavour is very pleasant, if a little sweet, and I now have no problem ingesting what I need to in order to gain weight. It may seem expensive, but at £2.50 a day it works out an easy, reliable and cost effective way to supplement your diet without resorting to less healthy alternatives. It works for skinny old me, and I don't see any reason why it shouldn't work for skinny old you! :)

Edit - it's now 22 days after I first used the product and I'm now just over ten stone, so that's 16lb in 22 days. People are commenting on the difference and it's done wonders for my energy levels and appetite. So all in all I can't recommend this product any more highly, it genuinely works. Can't say fairer than that!

Last update - I'm now at my target weight of 11st, it's taken 54 days for me to put on 30lbs - two stone two pounds in just under two months. That's beyond what I expected. If I could give a final note it would be to watch your body fat as without exercise this product will raise it quite easily. I'm now going to reduce my servings to maintain this weight, with my new increased appetite it's possible that I soon won't need a supplement at all. So that's me signing off, a bit heavier and a lot happier!

J
John S Durkin
Brilliant

I saw the reviews now I know why partly its got took be the best tasting protein drink I have ever had. I got the vanilla cream 2x tubs of it it's not thick so doesn't make you feel gaggy, if anything sometimes it's sweet and tastes like milky bar from KFC 2ndly I've tasted it now I will see if it works will edit and update soon

J
Justpoo
Effective product for underweight people

I've always been slim/athletic but after a serious illness I went under nine stone and stayed there (I'm five foot ten). I have a fast metabolism and eating the required amount of food to healthily gain weight was extremely difficult to sustain. I tried eating junky high calorie snacks but realised it was a stupid way of trying to gain weight.

So after buying this product I went straight in and tried to drink a full serving - mistake! I managed it but felt quite ill afterwards. I highly recommend you start with half or even a quarter serving to begin with, just until your stomach adapts. It's now two weeks later and with trial and error I've found that splitting a full serving into three is best for me. One in the morning, one after lunch, one in the evening. I use full fat milk, ice cream and a banana to boost the calories per full serving to over 2000, and I find a blender works great to give a nice semi-thick smooth shake.

When I started a fortnight ago I weighed 8 stone 12, I now weight 9 stone 8, so I've gained roughly 10 pounds in two weeks, with fluctuations along the way. I've just bought another 5.4kg bag and plan to continue to steadily gain until I reach around 11 stone. I bought some weights and with some advice I've started a light exercise programme with the aim of turning the energy to muscle and shaping my body a bit. I have more modest aims than many who take this supplement, I'm not looking to build huge muscles and train super hard, but if you're like me - underweight and a bit unfit - then I recommend this product along with some sort of exercise programme so it doesn't just go straight to your belly. It really does promote weight gain, I've been very pleasantly surprised with the results, and will continue to use the product as needed in order to achieve and maintain my target weight.

The chocolate flavour is very pleasant, if a little sweet, and I now have no problem ingesting what I need to in order to gain weight. It may seem expensive, but at £2.50 a day it works out an easy, reliable and cost effective way to supplement your diet without resorting to less healthy alternatives. It works for skinny old me, and I don't see any reason why it shouldn't work for skinny old you! :)

Edit - it's now 22 days after I first used the product and I'm now just over ten stone, so that's 16lb in 22 days. People are commenting on the difference and it's done wonders for my energy levels and appetite. So all in all I can't recommend this product any more highly, it genuinely works. Can't say fairer than that!

Last update - I'm now at my target weight of 11st, it's taken 54 days for me to put on 30lbs - two stone two pounds in just under two months. That's beyond what I expected. If I could give a final note it would be to watch your body fat as without exercise this product will raise it quite easily. I'm now going to reduce my servings to maintain this weight, with my new increased appetite it's possible that I soon won't need a supplement at all. So that's me signing off, a bit heavier and a lot happier!

E
Eager
Still seeing results

Great for muscle building, decent priced, lasts a while, flavour isn't the best but still good enough. Been using this for over 2 years now and still seeing results.

T
Toni Pinto
Was recommended

Was recommended this by a friend so I'll give it 5 star and update once a few weeks have past . I have lost 2 stone due to an illness and he recommended this product to get extra calories for weight gain . Used this himself to gain weight and I've seen the difference in him within 2 months . I'll mix with milk not water to bump the calroie intake up. Praying for the same results

V
Vincent Mak
Insoluble, large scoop but taste ok

Taste (chocolate) is ok, relative to other brands. However the scoop size is too large that unless has an electric blender, a handshake bottle won't fit and you’ll leave powder falling everywhere. Also it's not easily soluble, always lumps together, when comparing with other protein brands, not sure if it's common with mass gainers

V
Victor
Best protein in the market!

I have been using this protein for a long time now and its in my opinion one of the bests. I like the vanilla flavour which if you combine it with milk you barely notice is a protein shake, compared with other brands which can taste awful. I then add some strawberries and mix it together and it tastes even better than a strawberry milkshake from starbucks. Definitely recommend it after or before the gym and will get the calories going for a good bulk.

The only downside is it has many carbs but that's not any different with other protein brands.

A
A
Great for hard gainers

This product is great. Exactly what you would expect in a weight gainer; high calories, high carbs, quite high in protein. It is perfect for people trying to gain weight, who have a hard time struggling to get those extra calories from solid food. If you are a hard gainer this is a must. I gave this 4 stars, and not 5 for two reasons. First the taste is ok, but since you have to drink so much of it one go, it will kinda make you feel a little sick, and the after taste is not that nice either. Second if you are thinking about taking this in between meals think again. Lets say you take this after breakfast as a snack. Unless you have a super fast metabolism then you would have to wait a lonnng time till you are hungry enough to have lunch, which if you are a hard gainer is not a good thing. Even after a hard workout, where I was obviously hungry I still could not eat for at least 2 hours after taking this. So If you are thinking of taking this only once a day I would suggest taking it right before bed on your rest days, and once straight after your workout on your lifting days(which you should be doing if you a hard gainer). You should always eat solid food, before turning to supplements and if you skip lunch or dinner after taking this then it would be a meal replacement rather than a supplement.

E
Eager
Still seeing results

Great for muscle building, decent priced, lasts a while, flavour isn't the best but still good enough. Been using this for over 2 years now and still seeing results.

J
Jacek R
Best protein powder you can buy

It helps a lot. I gained 5kg in just one month with this wonderful product

S
Scott Evans
Great

Great product

J
Jacek R
Best protein powder you can buy

It helps a lot. I gained 5kg in just one month with this wonderful product

M
Monika
good product

amazing protein and very tasty

A
A
Great for hard gainers

This product is great. Exactly what you would expect in a weight gainer; high calories, high carbs, quite high in protein. It is perfect for people trying to gain weight, who have a hard time struggling to get those extra calories from solid food. If you are a hard gainer this is a must. I gave this 4 stars, and not 5 for two reasons. First the taste is ok, but since you have to drink so much of it one go, it will kinda make you feel a little sick, and the after taste is not that nice either. Second if you are thinking about taking this in between meals think again. Lets say you take this after breakfast as a snack. Unless you have a super fast metabolism then you would have to wait a lonnng time till you are hungry enough to have lunch, which if you are a hard gainer is not a good thing. Even after a hard workout, where I was obviously hungry I still could not eat for at least 2 hours after taking this. So If you are thinking of taking this only once a day I would suggest taking it right before bed on your rest days, and once straight after your workout on your lifting days(which you should be doing if you a hard gainer). You should always eat solid food, before turning to supplements and if you skip lunch or dinner after taking this then it would be a meal replacement rather than a supplement.

C
Caitlin Marie Sharpe
doesn't taste nice

doesn't taste nice

V
Victor
Best protein in the market!

I have been using this protein for a long time now and its in my opinion one of the bests. I like the vanilla flavour which if you combine it with milk you barely notice is a protein shake, compared with other brands which can taste awful. I then add some strawberries and mix it together and it tastes even better than a strawberry milkshake from starbucks. Definitely recommend it after or before the gym and will get the calories going for a good bulk.

The only downside is it has many carbs but that's not any different with other protein brands.

M
Marcin1988
Good quality, great price

very good suplement price-quality ratio

J
Jacek R
Best protein powder you can buy

It helps a lot. I gained 5kg in just one month with this wonderful product

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