One Week Flat Probiotics

28 sachets


(ex. tax)
4.4/5 (39 reviews) Read verified product reviews

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Suitable for



Gluten free

Gluten free

During pregnancy

During pregnancy

GMO free

GMO free

During breastfeeding

During breastfeeding



See full ingredients list


Optibac Probiotics One Week Flat is an easy seven-day course of probiotics and prebiotics, formulated to support digestive health, especially in those with occasional bloating*. Contains four high-quality probiotic strains which complement the natural gut bacteria.

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Probiotic Strains

  • Lactococcus lactis Rosell-1058
  • Lactobacillus casei Rosell-215
  • Lactobacillus acidophilus/helveticus Rosell-52
  • Bifidobacterium bifidum Rosell-71

Added nutrients

  • Prebiotic FOS
  • Product Description

  • How To Use

  • Ingredients

  • Help & Advice

  • Reviews

  • Delivery & Returns

  • Product Description

    Probiotics for occasional bloating*

    Key benefits

    • Specially formulated - for those who suffer from occasional bloating*
    • An easy, short-term option – designed to be taken over 7 consecutive days (1 sachet per day) 
    • Scientifically proven - to pass through stomach acidity and reach the gut
    • Quality, multi-strain formula – containing various high quality probiotic strains to support a healthy intestinal tract, digestion & aid transit*
    • Highly researched strains - such as L. acidophilus Rosell-52, found to support digestive enzymes including lactase & α-glucosidase, involved in the breakdown of lactose in milk & starch
    • 5 billion CFU + 0.3g prebiotic FOS (Fructooligosaccharides)  - the billions count is guaranteed until end of expiry
    • A more natural option - complements your natural gut bacteria, and free from artificial flavors often found in other food & drinks containing live cultures
    • Highly recommended - from the UK’s most trusted & recommended brand of friendly bacteria supplements. As determined in an independent survey of 1000 British women+.

    One Week Flat can be taken occasionally for 7 consecutive days once a month or on an ongoing basis.

    Product reviews


    Customer feedback collected via independent review platform Trustpilot. See more One Week Flat reviews for more customer opinions collected via our own website.

  • How To Use

    Recommended use

    Natural dietary supplement suitable for adults and children (from 4 years onwards) with the following recommendations:

    • Take 1 sachet daily for 7 consecutive days, preferably with breakfast.
    • Pour an inch of water into a tall glass, leaving plenty of room for swirling.
    • Shake the sachet before gently sprinkling the powder into the glass.
    • Vigorously swirl the water around in the glass making sure the powder is dissolved.

    We highly recommend you take One Week Flat for 7 consecutive days. Many consumers like to take this course once a month. However, it can be taken on an ongoing basis or as desired.


    • Store in a cool, dry place below 25°C (77 °F) and out of direct sunlight.

    Customer Questions

    All questions answered by probiotic experts Dr. Kate Stephens PhD (Food and Microbial Sciences) BSc(Hons) Medical Microbiology and Kerry Beeson BSc (Nutritional Medicine) Nutritional Therapist.

    Is One Week Flat suitable for both men and women?

    Definitely! Probiotics for the gut are not gender-specific, so One Week Flat is suitable for everyone over the age of 4 years who wishes to support occasional bloating, gut health, and digestion*. This includes men, women and trans and non-binary people, too!

    How often should I take One Week Flat probiotic supplements?

    It is recommended to take One Week Flat every day for at least one week. After that it is down to personal preference. One Week Flat can be used in the short term, as a week-long course for those experiencing occasional bloating* or if you are looking for an affordable way to 'top up' your gut bacteria every now and then. Equally, it can be used daily on an ongoing basis if you find this suits you best. There is no ‘right’ or ‘wrong’ way to take it. Here are some of the ways that our loyal One Week Flat customers take this supplement:​

    • A 7-day course regularly every month
    • A 7-day course as and when required
    • One sachet every day on an ongoing basis

    What does One Week Flat taste of?

    One Week Flat has a fairly ‘neutral’ taste and most people find it easy and pleasant to take. You may notice a slight natural sweetness which comes from the prebiotic fibers, but you can rest assured that the supplement contains no added flavourings, sugar, or sweeteners.

    I get bloated when I eat foods like dairy or gluten - can I take One Week Flat?

    One Week Flat is gluten-free so is fine to be taken by those with food-related bloating. It is also suitable to be taken by those with lactose intolerance1,2,3. It contains 4 well-researched probiotic strains combined with 0.3g FOS prebiotic fibers. Individual responses to a supplement can vary, but the majority of our customers get on very well with this formulation; in fact, some people find that probiotics, such as the Lactobacillus rhamnosus Rosell-11 strain in One Week Flat, help to improve digestion* of certain foods like dairy products1,2,3.

    I'm on a calorie-restricted diet. Can I take One Week Flat?

    One Week Flat contains just 7.72 calories per sachet, and 0g fat. Most of the carbohydrate in the supplement comes from the prebiotic fiber (Fructooligosaccharides, also known as FOS) which is not digested, and therefore has almost no calorific value. But the FOS feeds the friendly bacteria in our gut and helps them to flourish*.

    Does One Week flat help with occasional bloating?

    Many probiotic strains, including those found in One Week Flat, produce digestive enzymes. These digestive enzymes are known to help break down problematic foods, preventing excessive fermentation in the gut that can cause bloating4*. The good bacteria in the supplement also help to discourage the growth of undesirable bacteria5* which tend to product a lot of gases. For these reasons, many people find that One Week Flat can be helpful for occasional bloating*.​


    Probiotics are not recommended for those with serious medical conditions e.g. those who are severely immunosuppressed, have pancreatitis, are in the ICU, have melaena, have a central venous catheter, infants with short bowel syndrome, or patients with open wounds following major surgery; unless under a doctor's care. Keep out of reach of children.

    This is a dietary supplement and is not intended to prevent, treat or diagnose any medical conditions. Dietary supplements should not be used as a substitute for a healthy diet and lifestyle. If you are taking any medications or have a serious medical condition, consult a doctor before use. Optibac supplements will not cause dependency and may be used on an ongoing basis.


    1. Kocian J. (1996) ‘Further Possibilities in the Treatment of Lactose Intolerance: Lactobacilli’ Prakticky Lekar (General Practitioner). Vol. 74. pp. 212 – 214
    2. Rampengan et al., (2010), ‘Comparison of efficacies between live and killed probiotics in children with lactose malabsorption’. Southeast Asian Journal of Tropical Medicine and Public Health 41: 474-481​
    3. Oak SJ, Jha R. The effects of probiotics in lactose intolerance: A systematic review. Crit Rev Food Sci Nutr. 2019;59(11):1675-1683. doi: 10.1080/10408398.2018.1425977. Epub 2018 Feb 9. PMID: 29425071.
    4. D. H. Juers, B. W. Matthews and R. E. Huber, “LacZ β-galactosidase: Structure and function of an enzyme of historical and molecular biological importance,” Protein Science, vol. 21, no. 12, pp. 1792-1807, 2012.
    5. Likotrafiti E, Rhoades J. Probiotics, Prebiotics, and Synbiotics. Science Direct. Published 2016. Accessed September 30, 2020.

  • Ingredients


    Prebiotic FOS (Fructooligosaccharides 0.3g); Probiotic blend: Bifidobacterium bifidum Rosell-71, Lactobacillus casei Rosell-215, Lactococcus lactis Rosell-1058 and Lactobacillus acidophilus/helveticus Rosell-52; maltodextrin

    Each sachet guarantees 5 billion CFU + 0.3g FOS prebiotics.

    One Week Flat Supplement Fact Panel


    • Vegan
    • Vegetarian
    • Gluten free
    • Yeast free
    • No added sugar
    • GMO free
    • Suitable during pregnancy
    • Suitable during breastfeeding
    • Flavorless
    • Free from artificial flavorings, colorings and preservatives
    • No chemicals or parabens

    Following the taxonomic updates by a global team of scientists and published in April 2020, a reclassification has been advised for the L. casei species. The casei strain in the Optibac Probiotics One Week Flat product is now also known as Lacticaseibacillus casei Rosell-215.

  • Help & Advice

    Talk to our experts

    If you have a specific question or need some advice on which product to choose please email or click on the link below for our contact form

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  • Reviews

    Customer reviews

    • This product is a total game changer. I’ve tried all the opti bac products but this one seemed to agree with me the most and I now take these daily. The sachets make my bowels regular, which is something I’ve struggled with for years. The opti bac team have been great with their customer care and have been committed to helping me find a product that works for me. Thank you!

      Lauren - 1st March 2022

    • This is such a fantastic product to have in the cupboard for that time of the month bloating! I've suffered from bloating and flatulence in the week leading up to my period since I was in my teens. A friend of mine recently recommended 'One week flat', and it's really helped do just that. What a relief... thank you OptiBac Probiotics!

      Maria - 3rd May 2019

    • I gave birth to my 2nd child a little over two months ago and I’ve always had a little podgy stomach since I can remember. I have pcos which makes loosing weight a bit harder. I only lost half a stone since having my daughter, im now a size 10-12, 10 1/2 stone, I’m only 23 this year and have been doing exercises and eating more home made meals but I still feel so fat. I feel like it’s all mainly bloat though so I tried these and have been having two a day for the past wk to kick start it, maybe that’s why I didn’t see any different but I don’t think my stomach is any different. I’m going to buy one more box and try it one a day as it says as my body is quite arrogant and it’s hard to loose weight maybe one wk just isn’t enough, I’ve tried everything I really thought these would work and was really hoping they would.

      Jennie - 30th March 2019

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  • Delivery & Returns

    USA Shipping

    Coronavirus Update

    We ship all USA orders from our warehouse in Hampshire in the UK. Due to the ongoing global pandemic many US, European and Worldwide postal routes are seeing increased transit times. Delivery times provided on this site are therefore a guide and not a guarantee. Express Services largely remain unaffected however these routes are typically subject to local tax and duties at customs.

    USA standard shipping: $4.99

    International postal order - typically deatched and delivered within 5-10 working days.
    Free standard shipping on orders over $100.

    USA express shipping: $6.99

    We use DHL and orders are typically dispatched and delivered within 2-5 working days.



    Good to know

    • We'll send you an email to confirm once your parcel has been dispatched.
    • For delivery queries, please email
    • We are unable to ship orders to PO boxes.
    • Product prices on this website are always shown in US dollars (USD $) and exclude tax - tax is not applicable as orders are fulfilled from the UK.

    Worldwide Delivery

    • We deliver to more than 50 countries.
    • Shipping is charged at cost - please note that duties may apply.
    • Please allow 3-7 working days for delivery within Europe and 5-12 days to all other destinations. Includes order tracking.  
    • If you are located within the United Kingdom or Europe, we recommended switching to our UK website.
    • International deliveries might currently take a little longer due to the global coronavirus situation. Please refer to the webpage of our international delivery provider DHL to confirm the number of days it takes to receive your order and whether they currently ship to your country.
    • Most international delivery prices are dependent on the size and weight of your order and where it is being sent. You'll be shown the final price of shipping in the checkout, before payment, once we have your address and order details.
    • Long distance shipping and short-term exposure to high temperatures will not compromise the viability of our products. Customers living in very hot countries should store the products out of direct sunlight and refrigerate if the option is available.

    For more details regarding international orders, currency conversion and applicable tax for orders outside the USA, please take a look at our delivery FAQ.