What is St Mark's solution Dioralyte?: A Comparison of Clinical and Commercial Oral Rehydration

October 31, 2025 •

4 min read

Oral rehydration therapy is estimated to have saved over 70 million lives since its development in the 1960s. This simple, yet powerful treatment is available in various formulations, leading to questions like, "What is St Mark's solution Dioralyte?"—a query that reveals a key distinction between a specialized clinical treatment and a common over-the-counter product.

Quick Summary

This article explains the difference between St Mark's solution and Dioralyte, detailing their distinct compositions, clinical applications, and intended uses. It outlines why the high-sodium, potassium-free St Mark's mix is used for complex medical conditions like short bowel syndrome, contrasting it with the standard, commercially available Dioralyte for general dehydration.

Key Points

Specialized Clinical Use: St Mark's solution is primarily used for patients with high-output stomas or short bowel syndrome who require high sodium intake.
Homemade Formulation: Unlike Dioralyte, St Mark's solution is not commercially available and must be prepared daily from individual ingredients.
Potassium-Free: A key distinction is that St Mark's solution contains no potassium, which is critical for patients at risk of hyperkalaemia.
Commercially Available: Dioralyte is a common over-the-counter ORS used for general rehydration needs, such as during bouts of diarrhoea or vomiting.
Different Composition: Dioralyte's formulation includes potassium and has a lower sodium concentration than St Mark's, making it unsuitable for specific high-sodium requirements.
Clinical Guidance is Crucial: Patients with complex conditions should always follow medical or nutritional team instructions for ORS, as using the wrong solution can be harmful.

The Role of Oral Rehydration in Clinical Nutrition

Oral rehydration solutions (ORS) are vital for managing dehydration by replacing lost fluids and electrolytes. While many commercial products are available for general use, specific clinical conditions, such as intestinal failure or high-output stomas, require a specialized approach. These unique nutritional needs are the reason St Mark's solution was developed, setting it apart from standard preparations like Dioralyte. Understanding the differences is critical for ensuring patients receive appropriate care based on their specific health status.

What is St Mark's solution?

Developed at St Mark's Hospital in London, St Mark's solution is a potent, potassium-free ORS designed for patients with complex gastrointestinal conditions, most notably short bowel syndrome (SBS) and intestinal failure. SBS and related conditions impair the small intestine's ability to absorb water and electrolytes, leading to significant fluid and sodium loss. Regular ORS or plain water can worsen dehydration by drawing sodium from the body into the bowel, but the high sodium concentration in St Mark's solution counteracts this effect, boosting fluid absorption and minimizing fluid losses.

St Mark's solution is not available commercially; patients must prepare it fresh daily using a specific recipe. The ingredients are typically purchased from supermarkets or pharmacies. The standard recipe for one litre of solution includes:

20g of glucose powder
3.5g of sodium chloride (table salt)
2.5g of sodium bicarbonate (baking soda)

Patients are advised to sip the solution slowly throughout the day. Because the sodium bicarbonate can give the solution a bitter taste, chilling it, sipping through a straw, or adding a small amount of low-sugar squash can improve palatability. In some cases, sodium citrate is used as a substitute for sodium bicarbonate if the taste is intolerable.

What is Dioralyte?

Dioralyte is a brand of commercially available ORS sachets used for correcting fluid and electrolyte losses. It is widely used for treating dehydration resulting from diarrhoea, vomiting, or excessive sweating, such as during intense exercise. Dioralyte is formulated according to standard guidelines for general dehydration and includes a balance of key electrolytes, including potassium, which is not present in St Mark's solution.

Available in different flavours and formulations, such as Dioralyte Relief which contains rice starch to help harden stools, Dioralyte is intended for a broader range of patients, including adults and children. While effective for general use, its lower sodium content and inclusion of potassium make it unsuitable for the specific high-sodium, potassium-free requirements of patients with severe intestinal failure.

St Mark's vs Dioralyte: A Comparative Table


Feature	St Mark's Solution	Dioralyte
Primary Use Case	Clinical conditions like Short Bowel Syndrome, intestinal failure, and high-output stomas.	General dehydration from diarrhoea, vomiting, or exercise.
Availability	Prepared at home from individual ingredients; not commercially sold.	Commercially available in pre-measured sachets from pharmacies and supermarkets.
Sodium Concentration	High (approx. 90-120 mmol/L) to boost absorption in compromised intestines.	Standard (approx. 60 mmol/L in some formulations), sufficient for general rehydration.
Potassium Content	Potassium-free, crucial for patients at risk of hyperkalaemia.	Contains potassium (approx. 20 mmol/L), a necessary electrolyte for most people.
Preparation	Needs to be made fresh daily with accurate measurements of powders and water.	Simply dissolve one sachet in 200ml of water.
Taste	Can be salty or bitter, often needs flavouring additives like small amounts of squash.	Comes in pre-formulated flavours to improve palatability.

Preparation and Administration: The Critical Differences

Patient safety and treatment efficacy depend on understanding the distinct preparation methods for each solution. For St Mark's solution, precise measurement is non-negotiable. Using standard measuring spoons as directed by a healthcare professional is vital, as incorrect ratios can diminish its effectiveness. Drinking it chilled or through a straw can improve the taste, which can be challenging for some due to the high sodium content. Patients with intestinal failure should avoid drinking plain water or low-sodium fluids, which can exacerbate fluid loss.

Dioralyte, on the other hand, is a simple, ready-to-mix solution. The sachet's convenience makes it a quick and accessible option for addressing fluid loss. However, it's crucial to follow the instructions for reconstitution correctly to maintain the right electrolyte balance. Using the wrong amount of water will render the solution ineffective.

The Importance of Specialised Nutritional Guidance

The comparison between St Mark's solution and Dioralyte highlights the need for specialized nutritional guidance in clinical care. While Dioralyte is an excellent and readily available tool for managing common dehydration, it is not a substitute for the customized, high-sodium, potassium-free formula of St Mark's solution required by patients with intestinal failure. The development of solutions like St Mark's was a direct response to the inadequacy of standard treatments for a vulnerable patient population. Always consult a doctor or dietitian before choosing or preparing any ORS for a specific medical condition.

Conclusion

While both St Mark's solution and Dioralyte are oral rehydration therapies, they serve fundamentally different purposes and patient populations. St Mark's solution is a clinical-grade, homemade, high-sodium, potassium-free formula for managing severe intestinal fluid loss in conditions like short bowel syndrome. In contrast, Dioralyte is a commercially available, balanced electrolyte mix for treating standard dehydration from conditions like diarrhoea. The distinction underscores how a 'nutrition diet' can be a highly tailored aspect of medical care, moving beyond general advice to meet precise and life-sustaining needs. For further clinical guidance on St Mark's solution, resources from organizations like the NHS are invaluable.

Outbound link: Using St Mark's electrolyte solution – SPS

Frequently Asked Questions

The primary difference is their intended use and composition. St Mark's solution is a high-sodium, potassium-free, homemade mix for specific clinical conditions like short bowel syndrome. Dioralyte is a standard, commercially available ORS with lower sodium and added potassium for general rehydration.

Patients with a high-output stoma have greater fluid and sodium losses. Regular Dioralyte does not provide a high enough concentration of sodium to prevent further fluid loss and contains potassium, which could be problematic for patients at risk of elevated potassium levels.

To make one litre of St Mark's solution, dissolve 20g of glucose powder, 3.5g of table salt (sodium chloride), and 2.5g of baking soda (sodium bicarbonate) in 1 litre of cold tap water. The solution should be prepared fresh every 24 hours.

Yes, to counteract the salty taste, you can try chilling the solution, sipping it through a straw, or adding a small amount of low-sugar squash. A different ingredient, sodium citrate, may also be prescribed as a less bitter alternative to sodium bicarbonate.

No, St Mark's solution is a modification of the WHO ORS. The WHO solution includes potassium, while St Mark's is formulated to be potassium-free, making it more suitable for patients who require high sodium but need to avoid excess potassium.

Dioralyte is appropriate for general, less severe cases of dehydration from diarrhoea, vomiting, or exercise, particularly for individuals without complex gastrointestinal conditions. It is convenient for short-term fluid and electrolyte replacement.

If you have a chronic condition, such as short bowel syndrome, or experience persistent dehydration symptoms, you should consult your doctor or a clinical dietitian. They can provide a proper diagnosis and recommend the correct ORS formulation, such as St Mark's solution, tailored to your needs.

The solution can be stored in the refrigerator and any unused portion must be discarded after 24 hours, at which point a fresh batch should be prepared.