Rowan Bailey
24th September 2025
4C Ultra Sour 21% Medical Cannabis Strain Review UK
The first strain since RED No2 that hits the nose like a classic Super Lemon Haze. With impressive bold nugs and that familiar bold citrus terpene profile it's hard not to be excited when openning the pouch.
But does this transfer to the vape and effects? Jump into my in depth review to find out!
*Disclaimer*
Any experiences/ benefits described below are my own, and by no means should be taken as medical benefits / claims. This strain has been prescribed by my doctor for my specific condition and needs. It is important to talk to your Dr about your specific needs and see if they have other patients similar to you who have benefited from this strain or others. This post is purely meant as a useful reference for you to then do further research from. My tolerance, condition and experience will be greatly different to some.
Table of Content
- Introduction
- Main review
- Initial observation upon opening (nug shape/ density/ cure and shake content)
- Any improvement after storage change and curing?
- 4C Ultra Sour Strain effects
- Splitting the nug & under the scope
- How does it grind?
- Batch number
- Throat issues like scratching or allergies?
- Side effects or issues?
- Overall impression
4C Ultra Sour 21% Medical Cannabis Strain Review UK
Introduction
As mentioned in my other articles i've been impressed by the offerings from 4C over the last few months. Not just hearing great things from others, but from first hand experience trying their Sour Cherry Punch and Sudz.
So when I had to pick a replacement for one of my strains and Ultra Sour showed up, it was hard not to want to give it a go. Let's just so im very glad that I did. To find out why, continue reading below!
As always, if anyone has had this strain tested, or has sample COA that you think would be useful to attach here, please feel free to reach out and we’d be happy to showcase it here, along with any relevant reference back to you, and a cheeky gift card for our site as a thanks!
Main Review
Thanks for stopping by and checking out my review of the 4C Ultra Sour 21% Medical Cannabis Strain Review UK
This was sourced legally via prescription to myself with chronic pain being the primary condition this is used for. I hope my feedback here is useful for you to make an informed choice on future prescriptions, or to avoid it depending on your needs. I always welcome feedback in terms of other specific points I could cover in these reviews. Please keep in mind that i'm not a medical professional and these are no more than my personal anecdotal experiences.
The way this strain is being discussed is with relation to a chronic pain prescription relating to nerve pain and severe headaches, though it has also proven helpful beyond these treatments.
Continue to main review below!
The Best Dry Herb Vaporisers for Medical Cannabis in the UK: Our Picks
the best dry herb vaporisers for medical cannabis uk
What's the best dry herb vaporiser for UK medical cannabis? This is a tough question to answer, especially with so many choices ranging from £25 up to £500+!
We break down our top picks for medical cannabis dry herb vaporisers for UK medical cannabis to help you make the right choice first time!
As always if you need any help with medical cannabis supplies, finding out if your eligible or anything CBD related, let us know!
Device/ Setup
I now include my device setups so you can compare my feedback to what you use as everyones preferences are different.
Main devices:
Storz and Bickel Venty
Tinymight 2
Secondary Devices: Storz and Bickel Volcano Hybrid , Pax Plus & Dynvap M.
Outcome:
Ultra Sour comes in large beautiful nugs that break down easily. The grind is slightly coarser than other strains, but with little effort to get a finer grind if prefered.
The flavour on this strain bursts out at you with a gorgeous range of citrus and a subtle haze backdrop. The vapour is smooth with the well cured buds, but was a little on the dryer side of things compared to other 4C offerings. However not by much, and not as dry as a lot of medical cannabis comes.
Overall this vaped very well in both my Venty and Tinymight, but the flavour on the latter was unbeatable.
Anyway i'll jump into more detail down below on setup and how it vapes but on the whole this vapes well in all setups with a little more attention at the grinding stage.
Initial observation upon opening (nug shape/ density/ cure and shake content):
Immediate reaction was excitement at the incredibly familiar and bold terpene profile bursting with lemon.
The nugs were all considerable size with only a few in the bag. Well trimmed and cared for flower presented incredibly well with a medium to high density. Trichome coverage was decent with little to no disruption to external coverage.
Shake was non existent with nothing but large well formed buds in the bag.
Continue reading below!
Any improvement after storage change and curing?
My go to is to transfer my flower from the plastic tubs/ foil packs to UV protected glass storage (Whilst keeping original packs and labels on hand for verification and being out of the house!) in my opinion it just balances it out a little with the terps and helps any throat irritation that may occur. I have to avoid coughing and other things that can create intercranial pressure due to a brain op. As such trying to ensure the cure and setup for my vape minimises these chances are really important.
I'd say this strain arrived well cured even if slightly on the dryer side externally. This can easily be balanced with storage in a glass jar however.
The terpene profile on this is hard to miss so it requires little maintence to bring it out to it's best as it's most of the way there already.
Continued below!
Budget-Friendly Dry Herb Vaporizers Under £100: Top Picks for UK Vapers
Are you searching for the best cheap dry herb vaporizer in the UK? As a medical cannabis patient, I know how challenging it can be to find an affordable yet high-quality vaporizer. Everyone touts Tiny Mights and Mighty, but let's be honest, the prescription is expensive enough as it is and not everyone can afford to throw £300 at something like this.
Read More!4C Ultra Sour 21% Medical Cannabis Strain Review UK
Context: I’m prescribed for chronic nerve pain with severe headaches that is accompanied by nausea/ gastro issues at times. I work full time and have a young family. As such, I have to find the balance between managing pain/ symptoms, and being functional in my various responsibilities.
In turn, the split between a day time and night time strain gives me that ability to address deeper pains in the evenings where it may be more sedating, whilst using a more uplifting/ cerebral strain for day time to help get me through without any unwanted side effects. This has been key to me taking back my life and maintaining better quality of life all in.
Being a 21% strain Ultra Sour has been positioned to help find that balance between managing my pain but with produtivity intact. I have become used to having to find that balance with some strains impacting the latter, but that wasn't the case with Ultra Sour.
I found this strain to be one of the more dominant Sativa leaning options that i've had in a while. Which makes sense with its familiarities to Spectrum RED no2 from way back, and super lemon haze.
The bud formation shows a well cared for plant, and that carries through to the end user with the well intact terpene profile.
All in all i'm very impressed with this strain and would happily make it a staple, however sadly as I returned to order my next lot, it was no longer available... Whether it's been discontinued or is simply out of stock i'm not sure. What I will say is that if it does return and you like an old school Sativa, grab this up asap (But leave some for me!)
Continue reading below!
5 Quick Bits about 4C Ultra Sour
Who are 4C?
"Moving forward with a value-driven strategy. The 4C name was conceived from a value-first approach for our patients and doctors – which is why Care, Commitment, Choice and Change are more than just concepts to us; they are the very foundation on which our company was built.
This is reflected in the team that we have spent the last several years assembling that spans compliance, cultivation, technology, engineering and healthcare. A team with the sole focus of revolutionising medical cannabis for both patients and doctors in the UK.
UK patients deserve access to medicines that have been tested, certified and grown organically using proven cannabis genetics. With a deep understanding of plant genetics and innovative dosing strategies, 4C Labs delivers custom tailored solutions to address patients’ specific needs.
4C Labs’ cultivation strategy is spear-headed by a Canadian Master Grower with 25+ years experience supplying sought after products to compassion centres that serve the cancer community and others who suffer from chronic illnesses."
How Does It Grind?
Very well, the well formed buds break up really easily and grind with minimal effort. Though the nugs are moderately dense, they do breakdown into a coarse grind easily. Those who prefer a finer grind can easily achieve this with a couple of extra twists.
The grind reveals a well balanced cure internally with the terpenes bursting through ready for your vaporizer.
Batch No
For reference we usually include a batch number. Some strains have varied over time, often for the better. So we figured it's best to have a reference point for when we reviewed this for context.
This was from batch: BN:A335528
I've only had one batch of this strain before it went OOS. So I can't comment on consistency, however the batch I received was to a very high standard. It fits the price bracket well compared to other medical strains and I truly hope this returns soon as it's one of my favourite flavours to hit the UK market yet.
Throat issues/ catching/ allergies?:
In the past I have had hay fever like symptoms with a scratchy throat/ runny eyes and sneezing around loading my device or vaping certain strains. After a recent brain operation, avoiding coughing is a big priority for me to help reduce pressure. So I take note whether this is an issue on my reviews incase anyone else has the same problem!
I've not had any issues with this strain in terms of allergies or throat irriration. I've only had the one bag so can't say across the board, but I think it's safe to say this would be the case with other batches.
Continue reading below!
Strain Profile: 4C Ultra Sour 21%
Info from www.MedBud.wiki:
"Ultra Sour was created through crossing the powerful MK Ultra and East Coast Sour Diesel strains.
This bud has a super sour lemony diesel flavour and a spicy aroma to match. Ultra Sour buds have fluffy oversized bluish green spade-shaped nugs with bright fiery orange hairs and a coating of dusty amber coloured crystal trichomes."
Terpene profile:
Myrcene Minor Herbal/Musk 166-168℃
Limonene Minor Citrus/Sour 177℃
Caryophyllene Major Spice/Gas 119℃
Humulene Minor Earthy/Spice 107℃
Terpinolene Major Floral/Herbal 185℃
Guaiol Minor Woody/Rose 288℃
Consistency
I can't comment on consistency for this strain unfortunately as I have only had one lot through before it went out of stock.
However I will return here to comment should it return so that I can compare different batches.
Other Strain Reviews
Aurora Sourdough
A unique aroma that pleases the senses and soothes my symptoms with ease. This 29% strain has been making waves as it's difficult for pharmacies to keep it in stock, and with good reason.
This potent strain is ideal for my afternoon and evening doses when my back starts getting sassy.
Check out our review by click here!
Curaleaf LA Kush Cake
LA Kush Cake was a stable for me for a while. It's a strong strain with excellent bud structure and typically consistent from batch to batch.
At 25% it sits as one of the stronger options, but can be used to balance symptoms in the day in light measures!
Read more about what I thought here!
Wedding Pop Triangle (WPT)
I had no idea what to expect when this was added to my prescripton, but when I stuck my nose into the bag I was immediately transported back to Amsterdam in 2007. A familiar sour tone came flooding through backed up with some other familiar tones that I still cannot put my finger in. All in all I was really happy and the effects backed it up.
Sadly from batch to batch I haven't always had that same impactiful terpene profile, though effects have typically remained consistent. My recent two batches have been on point though!
Check it out under the microscope and my full review here!
Overall impression
This is another winner by 4C in my books, I just wish it was still available so I could order more.
I find this strain particularly helpful with managing my symptoms whilst retaining productivity in the day time. Those who like citrus strains will be a fan of this as the lemon comes through in abundance and transfers really well to vapour.
From the nug size, trim and form you can tell this has been well looked after from seed and it shows in terms of the end product. So if you see this pop back into stock, i'd suggest giving it a go.
On that note i'll be heading off. Thanks again for taking the time to read my review here, I hope it has helped in some way to shed light on what to expect with this strain.
As always I really appreciate the support and the time taken by our readers to checkout our content, so thank you!
Take care!
- Rowan
Meet the reviewer
Rowan is one of the founders of Infinity CBD and Pembrokeshire CBD Centre. Having worked in the CBD/ Cannabis industry for over five years, he has extensive knowledge of the supply chain issues, compliance and other fun things you have to contend with from the corporate side of all of this. However, having also been a patient for 4+ years he has also seen first hand of the ups and downs of the patient experience, quality woes and what to generally expect.
These medical cannabis reviews are presented to try and form a balanced and honest opinion relating to his experience and understanding of the limitations the clinics/ pharmacies and producers face with trying to navigate compliance standards that compete with perceived quality of some products.
Everyone is different, and Rowan is prescribed for specific conditions and is provided these prescription legally by a Dr who has been working alongside him to find the best treatments. This means that any perceived benefits expressed in his article are purely anecdotal and related to his experience and may not reflect yours and certainly in no way mean to boast any medical claims about the use of these treatments outside of what he has personally experienced.
“Medical cannabis has given me back control and vast improvement in terms of my quality of life day to day. Although I still struggle with my symptoms, this has enabled me to still be present and functional on the worse days, and given the peace of mind that knowings it's there if I need it on the better ones.”
- Rowan Bailey
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