One Week Flat Probiotics

28 sachets |4 weeks' supply

Camilla Gray DipCNM Nutritional Therapist
My personal discovery of live cultures started with One Week Flat 10 years ago and it’s one I still use and recommend regularly, especially before holidays or festive periods.
Camilla Gray
Camilla Gray DipCNM Nutritional Therapist

Who is it for?

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

Buy online from our UK website
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  • Vegan


  • Gluten free

    Gluten free

  • GMO free

    GMO free

  • No added sugar

    No added sugar

Key benefits

Probiotics for occasional bloating*

A short-term probiotic supplement formulated to complement the natural gut bacteria.

  • Specially formulated probiotic Ideal for those who suffer from occasional bloating*
  • High-quality supplement Contains strains proven to survive stomach acidity and reach the gut alive
  • Using only targeted strains Including Lactobacillus acidophilus/helveticus Rosell-52
  • Synbiotic formula with prebiotic FOS A multi-strain supplement containing four probiotic strains combined with prebiotic FOS
  • Helps to get you party ready A great supplement to take in advance of weddings, festivals and holidays!
  • Easy to take and flavourless Individual powder sachets can be mixed into cool, non-acidic food or drink
  • Can be taken ongoing Ideal for occasional use, simply take for at least 7 consecutive days, or can be taken daily
  • The UK's most recommended brand Optibac is the brand of probiotic supplements most recommended by UK consumers

Probiotic strains

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

Added nutrients

  • Prebiotic FOS
See full ingredients list

Complements gut bacteria


General digestive

Customer Reviews

Customer reviews have been collected on our website or independently through Trustpilot where no moderation is possible. Reviews are not endorsed by us and should not be regarded as medical or health advice. For supplement advice, you can speak to one of our qualified experts. The top 3 reviews have been selected from our website, please click view all to explore more customer feedback.

Help & advice

Our team of qualified experts are available for free personalised supplement advice. If you're not sure where to start or your needs have recently changed, please get in touch.

Louise Mason
Louise Mason BA(Hons) DipCNM Nutritional Therapist, DipCNM Naturopath, mANP
  • How to use

  • Ingredients

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  • Delivery & returns

  • 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.


    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.

    Gut health supplements are not intended to prevent, treat or diagnose any medical conditions. If taking probiotic supplements for gut health, note that these should not be used as a substitute for a varied and balanced diet and a healthy 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.

    Format Sachet
    CFU 5 billion
    Added Ingredients FOS Fibres
    Recommended Use 1 sachet daily
    Age Range Adult
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  • Delivery & returns

    USA standard shipping: $4.99 

    International postal order - typically deatched and delivered within 5-10 working days.
    Free standard shipping on orders over $60.

    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.


    If you have changed your mind, you can return goods, at your cost, unopened within 14 days for refund or exchange, this does not affect your statutory rights.

Customer Questions

All questions answered by probiotic experts Dr Kate Stephens PhD (Food and Microbial Sciences) BSc(Hons) Medical Biology and Louise Mason BA(Hons) DipCNM Nutritional Therapist, DipCNM Naturopath, mANP

Many probiotic strains, including those found in Optibac Probiotics 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 bloating1*. The good bacteria in the supplement also help to discourage the growth of undesirable bacteria2* which tend to product a lot of gases. For these reasons, many people find that One Week Flat can be helpful for occasional bloating*.​

Read references

Initially it’s best to take Optibac Probiotics One Week Flat daily for one week to complement and balance your natural gut bacteria*. After that, people take a week’s course every month, or whenever they feel they need support for occasional bloating*. Others prefer to take one sachet every day on an ongoing basis. All of these options are absolutely fine! See what suits you best.

Optibac Probiotics One Week Flat is dairy and gluten-free, so is fine to be taken by people who suffer with food-related bloating or lactose intolerance1,2,3. This high-quality supplement contains four, highly researched probiotic strains combined with natural prebiotic FOS fibres, which together help to support the gut microbiome and gently help you to more easily digest problem foods*.

Read references

With only 7.72 calories per sachet, and 0g of fat, it’s easy to include Optibac Probiotics One Week Flat in your calorie-controlled diet. The carbohydrate content is mostly natural FOS fibres which indigestible and have barely any calorific content.

Definitely! Probiotics for the gut are not gender-specific, so Optibac Probiotics 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!

Yes! Optibac Probiotics One Week Flat is carefully formulated to have a slightly sweet, ‘neutral’ flavour which most people find pleasant to take. However, be reassured that the supplement contains no added flavourings, sugar, or sweeteners – the mild sweet taste comes from the natural Fructooligosaccharide (FOS) fibres.

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