How much water does it take to overdose

Ever heard of hyponatremia? It’s a fancy word for water intoxication, and it happens when you drink too much water.

It seems people everywhere are constantly reminding us: “You need to drink more water.” So how in the world does overhydration even happen?

Balance in the body

Well, it all comes down to sodium levels. The sodium in our body has the job of balancing fluids in and around the cells, according to the National Institutes of Health. Drinking too much water can cause an imbalance, forcing the liquid to move from your blood to inside your cells, making them swell. Swelling in the brain can be serious and sometimes fatal. It can also trigger seizures and coma.

In addition, your kidneys filter everything you drink and make sure the fluid levels in your bloodstream stay balanced. When you drink too much water, it makes your kidneys work overtime, leaving your body stressed and fatigued.

How much is too much?

So how much water is too much? To be clear, it would take a lot (times a lot) for someone to suffer from water intoxication. We’re talking about an intake of gallons of water. The fatal cases are isolated, and extremely rare.

What about someone who's especially active, like, say, training for a marathon? Or a woman who is pregnant or nursing a child? Take heart in knowing that people in different circumstances do require a higher intake of water.

In reality, the majority of people tend to have a problem with dehydration rather than overhydration.

“Young, healthy people don’t normally (get hyponatremia) unless they drink liters and liters of water at once, because your kidneys can only (expel) about half a liter, at most, an hour,” said Chris McStay, an emergency medicine doctor. “You’re drinking more than your kidneys can pee out.”

Similarities to dehydration

The ironic thing about being overhydrated is that a lot of the symptoms are much the same as being dehydrated.

“It’s often hard to tell the difference … between water intoxication and heat exhaustion, unless you know they drank 6 gallons of water," McStay said.

So what are some signs you may be drinking too much water?

What’s the right amount?

Having said all this, it begs the question: How much water should one be drinking in a day?

Unfortunately, there isn’t an exact recommended daily allowance for water consumption.

Ultimately, the consensus among experts is to drink until you don’t feel thirsty, then stop.

McStay said a good way to tell if you need to drink more water is to take a look at your urine. If it’s dark, you’re probably dehydrated, and you should drink.

For those who are more active, sometimes it helps to have sports drinks, which contain more electrolytes. However, it’s worth noting that you want to pay attention to the amount of sugar in the drinks, which experts recommend should be about 5 grams per 8-ounce serving.

But if you really want a hard number to start with, experts at the Mayo Clinic say a goal of eight glasses a day is reasonable for a sedentary person. However, you will likely need to modify your intake if you’re exercising, sick, pregnant or breastfeeding, or live in a hot or humid area or at a high altitude.

1Department of Histopathology, Torbay Hospital, Lawes Bridge, Torquay, Devon, TQ2 7AA, UK; [email protected]

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L Bower

2Department of Clinical Chemistry, Torbay Hospital

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1Department of Histopathology, Torbay Hospital, Lawes Bridge, Torquay, Devon, TQ2 7AA, UK; [email protected]

2Department of Clinical Chemistry, Torbay Hospital

Keywords: fatal, intoxication, water

Water intoxication can occur in a variety of different clinical settings but is generally not well recognised in the medical literature. The condition may go unrecognised in the early stages when the patient may have symptoms of confusion, disorientation, nausea, and vomiting, but also changes in mental state and psychotic symptoms. Early detection is crucial to prevent severe hyponatraemia, which can lead to seizures, coma, and death.

The patient reported here was a 64 year old woman with a known history of mitral valve disease but no other relevant past history. On the evening before her death, she began compulsively drinking water in vast quantities, estimated at between 30 and 40 glasses, and this was interspersed with episodes of vomiting. She became hysterical and also distressed, shouting that she had not drunk enough water. She declined medical attention but continued to drink water after she had gone to bed. She later fell asleep and died some time later.

A postmortem examination was carried out six hours later. The pituitary and adrenal glands were normal and there was no evidence of a bronchial tumour. There were bilateral pleural effusions of 200 ml on each side and the cut surfaces of the lungs (568 g and 441 g) exuded frothy pink fluid. The heart (461 g) showed evidence of mitral valve disease and left ventricular hypertrophy. Within the stomach there was 800 ml of watery fluid and the intra-abdominal organs were generally wet.

Postmortem toxicology was negative. A sample of vitreous humour showed a sodium concentration of 92 mmol/litre (serum reference range, 132–144). Potassium, urea, and glucose were all within the serum reference ranges. Blood cortisol was raised, excluding an addisonian crisis.

The cause of death was given as hyponatraemia as a result of acute water intoxication.

Water intoxication provokes disturbances in electrolyte balance, resulting in a rapid decrease in serum sodium concentration and eventual death. The development of acute dilutional hyponatraemia causes neurological symptoms because of the movement of water into the brain cells, in response to the fall in extracellular osmolality. Symptoms can become apparent when the serum sodium falls below 120 mmol/litre, but are usually associated with concentrations below 110 mmol/litre. Severe symptoms occur with very low sodium concentrations of 90–105 mmol/litre. As the sodium concentration falls, the symptoms progress from confusion to drowsiness and eventually coma. However, the rate at which the sodium concentration falls is also an important factor, and the acute intake of large volumes of water over a short period of time, as occurred in this case, would have produced a rapid drop in serum sodium, which was fatal.

Postmortem serum samples are unsuitable for sodium measurement because concentrations decrease after death and there is considerable individual variation. However, vitreous sodium concentrations are stable in the early postmortem period, and the concentration in vitreous humour is similar to that found in normal serum.1 Studies have shown that abnormal vitreous humour sodium concentrations had corresponding antemortem hyponatraemia or hypernatreamia.2

Self induced water intoxication is known to psychologists, but there is a paucity of information and little awareness of this life threatening problem in the professional literature.3 The initial symptoms associated with this condition are very similar to psychosis, with inappropriate behaviour, delusions, hallucinations, confusion, and disorientation.4 If untreated, the symptoms may progress from mild confusion to acute delirium, seizures, coma, and death, as occurred in this case.

Fatal water intoxication has been described in several different clinical situations. The most common of these is psychogenic polydipsia (compulsive water drinking), which is sometimes associated with either mental illness or mental handicap.4,5 The condition has also been described in young army recruits of good health who developed hyponatraemia after apparent overhydration following heat related injuries.6 The most common symptoms suffered by this group were changes in mental status, emesis, nausea, and seizures. Accidental water intoxication has been described as a result of excessive water intake after an episode of gastroenteritis,7 and an iatrogenic case has occurred after gastric lavage.8 Forced water intoxication is a recognised form of child abuse, which commonly leads to brain damage and is sometimes fatal.9

In conclusion, we wish to highlight an unusual cause of death that may go unnoticed without an appropriate clinical history and relevant postmortem biochemical investigations. Both clinicians and pathologists need to be aware of this condition, which may manifest itself as a psychotic illness and so go unrecognised in its early stages. Early detection is crucial to prevent fatal complications.