Polydipsia: Pica’s Lesser Known Sister
Cite this article as: Batalla-Duran, L. (2026). Polydipsia: Pica’s lesser known sister. Ability Bridge SEND. https://www.abilitybridgesend.co.uk
Why polydipsia remains pica’s lesser known sister
Pica is poorly understood. Just a decade ago almost no one in special education had heard of it, where it was often described simply as “they put anything and everything in their mouths.” Pica awareness and understanding is slowly growing but polydipsia still remains largely hidden. Polydipsia is well recognised in psychiatric services, yet it rarely crosses into the threshold of education. In schools, homes and care settings it is often missed, misinterpreted or seen only as “at least we don’t have to worry about their hydration, they drink plenty,” without any understanding of the underlying safeguarding issues or unmet need.
Why polydipsia is so often missed
Polydipsia is frequently overlooked because parents, education staff and even health professionals are consistently taught that hydration is positive. Of course, there is little doubt that hydration is important, linked with reduced constipation, better digestion, temperature regulation, stable blood pressure, improved concentration, fewer headaches and general wellbeing. However, there is a fairly fine line between being well hydrated and becoming critically unwell from low sodium levels.
For pupils who have a typical SEND beige diet, limited exercise and spend little or no time outside, adults are often relieved that at least they drink plenty. With this messaging, excessive drinking is usually interpreted as healthy rather than a sign of unmet need. What is rarely taught or highlighted is that drinking too much water can dilute sodium levels and lead to hyponatraemia, which can cause serious illness and, in some cases, can be fatal. Because this risk is not routinely covered in training or public health messaging, polydipsia is frequently overlooked, misinterpreted or seen only through a harmless behavioural or sensory lens instead of being recognised as unmet need and a potential safeguarding concern.
Dangers of polydipsia
Healthy adult kidneys can clear around 0.8–1.0 litres of water per hour. Drinking more than this can overwhelm the kidneys and dilute sodium levels. Low sodium levels affect the brain first, and symptoms usually progress from mild dizziness and nausea to confusion, headaches and vomiting, then seizures, coma and, if not treated, can be fatal.
Children have significantly smaller kidneys, so they cannot clear anywhere near this amount. Because of this, children drinking excessive volumes of water can develop symptoms much more quickly, and presentations related to over‑drinking are not uncommon in Accident and Emergency departments (Royal College of Emergency Medicine, 2023).
It is not inconceivable that a proportion of children and young people in our settings are consuming what adults around them perceive to be an appropriate amount of water, yet are in fact drinking enough to lower sodium levels without triggering concerns about acute water intoxication. In some cases, this reduction in sodium may be causing dizziness, confusion and cognitive impairment, potentially affecting daily functioning and learning.
In special schools, there can be a natural tendency to normalise behaviours that would warrant attention elsewhere. Licking soap from hands, consuming small amounts of PVA glue or art paint, or sucking up shaving or washing-up liquid foam can become so familiar that the significance of these behaviours is overlooked. Whilst these behaviours rarely result in acute poisoning, the repeated ingestion of soaps, cleaning products, adhesives and other non-food items may contribute to ongoing exposure to substances that the body was never intended to process, creating health risks that can easily be underestimated.
Increased, prolonged or recurring urinary tract infections (UTIs): When too much liquid is consumed, the bladder becomes overstretched and cannot empty fully, leaving urine behind; this leftover urine gives bacteria a warm place to grow, increasing the risk of UTIs. Children are more vulnerable because their bladders and pelvic muscles are smaller and still developing (NHS, 2024; Mayo Clinic, 2024).
Polydipsia may begin with drinking large amounts of water, but for some individuals the drive to drink becomes so strong that they seek out unsafe sources such as toilet water, puddles or bath water, and in some cases harmful liquids like cleaning fluids. This escalation is usually the point at which polydipsia is recognised as a concern. For many of our our children and young people, they are likely unaware of the dangers of cleaning fluids and so do not discriminate between a water bottle or a bottle of washing-up liquid. There is also the salient issue that brightly coloured cleaning fluids can easily be mistaken for soft drinks, making them more appealing than water, increasing the risk that they will be consumed.
This of course brings a new safeguarding concern: poisoning, burning and chemical injury from ingesting harmful liquids.
Colourful cleaning products at a market which could easily be mistaken for soft drinks.
How hidden polydipsia can be
A couple of years ago, I ran a pica and polydipsia course for Unique | Understanding Rare Chromosome and Gene Disorders. A colleague, a health professional, came into my office super excited because my talk had appeared in her feed. She said she knew what pica was but had never heard of polydipsia, so I explained it. Straight away she questioned whether her own daughter might have polydipsia, as she had always drunk very large amounts of liquid. As a baby she would take bottle after bottle of milk and water and developed UTIs from a young age, and this continued into her teens. Her doctor kept encouraging her to drink more, but, as a health professional, my colleague believed this was making the UTIs worse, and she had tried to reduce how much her daughter drunk, estimating she was easily consuming around five plus litres of water a day. She asked me what might cause her urge to drink. Knowing her daughter and the unmet needs associated with polydipsia, I suggested anxiety being the cause but encouraged her to ask her daughter (an intelligent teenager) directly as it is easy to forget pupil voice and advocacy.
The next morning she came back and said her daughter had confirmed that her anxiety caused her to drink, explaining that when she feels anxious, she gets a strange feeling in her throat, and drinking water takes that feeling away and calms her. We talked about ways of managing the anxiety and about putting as much ice as possible in the water bottle, which provides calming cold sensory input to the vagus nerve.
NB - Adding ice to drinks reduces the overall volume consumed and slows down the speed at which it is drunk. It’s the long‑standing “oldest trick in the money‑saving book” in hospitality and the first thing you are taught behind the bar (add ice = add profits). Contextually, it can be genuinely helpful for children and young people who drink very large amounts very quickly, as it naturally slows their drinking and reduces the quantity consumed.
Recognising polydipsia early, before it becomes a near miss
Polydipsia remains largely unseen in education and health outside of psychiatric settings because high drinking is usually viewed as positive, and the risks are rarely known. What begins as drinking large amounts of safe liquids can develop into a pattern that affects sodium levels, bladder function and overall safety, yet it is often only recognised once unsafe liquids are sought. By understanding the early signs of polydipsia and the unmet needs that drive it, we can identify polydipsia before it reaches the point of harm and give our children and young people, their parents and carers, and us as educators the support we all need.
If you’d find it helpful to explore the topic of pica and polydipsia further, I’ve created a needs‑led online course for schools. You can access it here:https://louise-s-site-a81e.thinkific.com/products/courses/pica-polydipsia-school-training
NHS. (2024). Urinary tract infections (UTIs). https://www.nhs.uk/conditions/urinary-tract-infections-utis
Mayo Clinic. (2024). Urinary tract infection (UTI). https://www.mayoclinic.org/diseases-conditions/urinary-tract-infection/symptoms-causes/syc-20353447
Royal College of Emergency Medicine. (2023). Paediatric emergency guidance: Hyponatraemia. https://rcem.ac.uk
