Electrolytes: What They Do, Signs of Imbalance and When to See a Doctor

Electrolytes are salts dissolved in the body's fluids, and their levels must stay within narrow limits for muscles, the heart and the nervous system to work properly. When sodium, potassium, calcium or magnesium rise or fall too far, the result can range from tiredness and muscle cramps to confusion and, in serious cases, heart rhythm problems. Most often the cause is fluid loss through vomiting, diarrhoea or heavy sweating, but kidney disease, hormonal conditions and some medicines can also upset the balance. This guide explains what electrolytes are, what they do, how an imbalance shows itself, how it is treated and when it needs medical attention.

What electrolytes are and what they do

What are electrolytes, in the plainest terms? An electrolyte is a substance that splits into electrically charged particles, called ions, when it dissolves in water. In the body the main electrolytes are sodium, potassium, calcium, magnesium, chloride, phosphate and bicarbonate. They are found both inside cells and in the fluid surrounding them, and the difference in concentration between the two sides is what allows nerve cells and muscle cells to function.

What do electrolytes do in practice? They help nerves send signals, make muscles contract and relax, keep the heartbeat regular and control how water is distributed between the blood, the tissues and the cells. They also help keep the acidity of the blood within a safe range. None of this is something a healthy person has to think about, because the body regulates it automatically.

The kidneys do most of the regulating. They decide how much of each electrolyte leaves the body in the urine, while hormones steer thirst and the retention of water and salts. This system copes well with ordinary variation in food and drink from one day to the next.

Electrolytes and body water are closely linked. The sodium level in the blood, for example, tells mainly about how much water there is in relation to sodium. For this reason, electrolyte problems are almost always considered together with fluid balance.

The main electrolytes and their roles

Each electrolyte has its own job, and they influence one another. Potassium and magnesium, for instance, both take part in keeping the heart rhythm steady, while sodium governs how much fluid the body holds. The four described below are the ones whose disturbances are most often seen in everyday life and in medical care.

Sodium

Sodium is the main electrolyte of the fluid outside the cells. It controls how water is distributed in the body and takes part in the transmission of nerve impulses. The normal blood level in adults is about 137 to 145 mmol/l, and it reflects water balance more than it reflects how much salt a person eats.

Potassium

Potassium sits mostly inside the cells, and only a small share is found in the blood. Even so, it is crucial for the function of muscles and above all the heart muscle. The adult reference range in blood is roughly 3.3 to 4.9 mmol/l, although laboratories may set slightly different limits.

Calcium

Most of the body's calcium is stored in the bones, and only a small amount circulates in the blood. The parathyroid glands and vitamin D keep the blood level tightly regulated. The normal total level in blood is about 2.15 to 2.51 mmol/l, and calcium affects muscle contraction, nerve function and heart rhythm.

Magnesium

Magnesium takes part in hundreds of metabolic reactions. The body holds about 20 to 28 grams in total, more than half of it in the bones, so less than one percent is found in the blood. The normal blood level is around 0.71 to 0.94 mmol/l.

Signs of electrolyte imbalance

A mild imbalance is often completely silent and is found by chance in a blood test. A slightly low sodium level of 130 to 135 mmol/l, for example, usually causes no symptoms. Symptoms appear when the change is larger or develops quickly, and they depend on which electrolyte is affected.

Common signs include tiredness, weakness, headache, nausea, muscle aches and muscle cramps. When sodium falls clearly, confusion can appear, and in severe cases seizures. Low potassium can cause muscle weakness, fatigue and constipation and raises the risk of heart rhythm disturbances. High potassium may cause fatigue, muscle weakness and odd sensations in the limbs.

Low calcium can cause tingling in the fingers, toes and around the mouth, along with muscle cramps. High calcium may show as tiredness, loss of appetite, stomach symptoms, poor concentration and confusion. A shortage of magnesium can cause muscle weakness, cramps, tremor and rhythm problems, and in a severe shortage seizures.

None of these signs belongs to one electrolyte alone, and the same symptoms have many other causes. A single cramp or a tired afternoon does not mean that the balance of electrolytes is off. If several symptoms occur together, last for a long time, or appear alongside vomiting, diarrhoea or a chronic illness, it is sensible to have them checked.

Causes of electrolyte imbalance

The most common cause is loss of fluid and salts. Prolonged vomiting or diarrhoea removes water, sodium and potassium from the body, and if drinking does not keep up, the levels begin to shift. Heavy sweating in hot weather or during long exertion can do the same, especially if little is drunk or if very large amounts of plain water are taken.

The kidneys play a central role, which makes kidney disease one of the key causes. When the kidneys cannot remove potassium properly, the blood level can rise, and kidney disease is the most common reason for high potassium. Acute kidney injury can also develop as a result of dehydration, and at first it is usually without symptoms, so it is found through laboratory tests.

Medicines can affect electrolytes in several ways. Diuretics, sometimes called water pills, are the most common cause of low potassium, and some can lower sodium as well. Certain blood pressure and heart medicines, and some medicines used for epilepsy and depression, are known to influence sodium or potassium levels. Medicines should never be stopped without advice, and any concern is best discussed with a doctor who can assess the situation individually.

Calcium and magnesium have their own typical causes. Severe vitamin D deficiency, absorption problems such as coeliac disease, and advanced kidney disease can lower blood calcium, while an overactive parathyroid gland is the most common reason for high calcium. Magnesium deficiency is most often linked to absorption problems, diuretics, heavy alcohol use, kidney disease, poorly controlled diabetes, prolonged diarrhoea or long-term use of acid-reducing medicines. Diet alone rarely explains these situations.

Hormonal conditions are also on the list. Underactive adrenal glands can raise potassium, and eating a lot of liquorice can lower it. Severe undernutrition, including eating disorders, can lead to low potassium as well.

Sodium can also fall because too much water stays in the body. Heart or kidney disease, certain cancers, and strong nausea or pain can increase the release of antidiuretic hormone, which makes the body hold on to water. A healthy person with normal kidneys can handle several litres of water a day when it is spread over many hours, but drinking a very large amount quickly can dilute the sodium in the blood.

Dehydration and electrolytes

Dehydration means that the body loses more fluid than it takes in. Salts leave with the fluid, so dehydration is nearly always also a challenge to the balance of electrolytes. Typical causes are vomiting, diarrhoea, fever, heavy sweating, too little drinking and, in diabetes, high blood sugar that increases urine output.

A high blood sodium level usually means there is too little water in relation to sodium, not that someone has eaten too much salt. Mild dehydration is felt as thirst, a dry mouth and darker urine. In more severe cases there may be muscle twitching, confusion and seizures, and a sodium level above 155 mmol/l is a serious situation.

Older adults may feel thirst less strongly, and small children cannot say that they are thirsty, so dehydration can progress unnoticed in both groups. In a child the signs include dry lips and mouth, a sunken soft spot on the head in babies, passing urine less often, and drowsiness or floppiness. In a small baby, more than four to six hours without a wet nappy is a reason to seek care.

In hot conditions the loss of fluid and salts can lead to heat exhaustion and, in the worst case, heat stroke. Warning signs include weakness, nausea, confusion and especially dry skin, which suggests that sweating is failing. Thirst is not a reliable guide, so drinking regularly and watching the colour of the urine helps.

During sport and heavy outdoor work, sweating removes fluid and salts for hours. A short workout is usually managed without any special measures, but a long, hot and strenuous effort can drain the body's reserves. Cramping, dizziness and unusual fatigue during exertion are signs that rest, a break and drinking are called for.

Electrolytes blood test: when levels are measured

Electrolyte balance is assessed with a blood test that typically measures sodium and potassium and, when needed, calcium, magnesium and other values. Creatinine, which reflects kidney function, is often measured at the same time. An electrolytes blood test is a way to see whether fluid balance or kidney function has been disturbed, even when symptoms are mild.

The test is used when vomiting or diarrhoea is prolonged or severe, when dehydration is suspected, and when symptoms include confusion, muscle weakness or heart rhythm disturbances. It is also taken when a person uses diuretics or other medicines that affect electrolytes, and to follow kidney and hormonal conditions. In hospital, the values are checked repeatedly because fluid treatment changes them.

The sample is usually taken from a vein. Kidney function is assessed with creatinine and a urine test, because the kidneys regulate electrolytes. In severe disturbances a doctor may also check the heart rhythm, as potassium and calcium affect how the heart works.

The result is always interpreted together with symptoms, illnesses and medicines. A small deviation may need nothing more than follow-up or looking into the cause. With magnesium, the blood level can be normal even when the cells are short of it, so the result does not always tell the whole story.

Treatment of electrolyte imbalance: fluids, food and hospital care

Treatment depends on which electrolyte is out of balance, how severely and why. The first step is always to identify and treat the underlying cause. A mild disturbance often corrects itself once vomiting or diarrhoea has passed and fluid intake returns to normal.

In mild dehydration, replacing fluids by mouth is the main treatment. According to clinical health guidance, the most important thing in acute diarrhoea is to replace lost fluid as it is lost. Water, diluted juice, tea, broth and milk are suitable, and a little salt can be taken in lightly salted food. Drinking large amounts of very sugary drinks alone can make diarrhoea worse, because sugar draws water into the bowel.

Ready-made oral rehydration solutions that contain salts and glucose also exist, and they are used for treating and preventing dehydration. They replace lost salts as well as fluid, and they are used particularly in children and when diarrhoea continues. How suitable a solution is, and how much to take, depends on age and the situation, and in unclear cases advice from a healthcare professional is worth asking. Eating is allowed if there is an appetite, since food does not make diarrhoea worse, and breastfeeding continues.

More severe disturbances are treated in hospital. Intravenous fluids correct a shortage of water and salts, and electrolytes can be given into a vein under close monitoring when needed. When sodium is too low, treatment depends on the cause: salt loss is corrected with saline solution, whereas holding on to too much water is treated with restricting fluids and treating the cause. Correcting levels too quickly can be dangerous, which is why high sodium, for example, is brought down slowly.

For potassium, calcium and magnesium, treatment also depends on the cause. A low level can be corrected by mouth or into a vein, and severe cases are treated in hospital. A high potassium level that is severe needs hospital care, and in kidney disease dialysis may be required. High calcium is treated by addressing its cause, such as an overactive parathyroid gland. Whether any supplement or medicine is suitable is always decided individually by a doctor.

Food and drink as sources of electrolytes

An ordinary varied diet covers the electrolyte needs of a healthy person. Magnesium comes from grain products, vegetables, potatoes, fruit and berries, and also from coffee, mineral water and dairy products. Calcium is found especially in dairy foods, and potassium in many vegetables, root vegetables, fruit and berries. Sodium comes mostly from the salt in food.

According to clinical health sources, a poor diet rarely causes an electrolyte disturbance in a healthy person. In a healthy person, for instance, the blood potassium cannot become too high from food, because the kidneys remove the excess. A shortage of magnesium from diet alone is extremely rare, and the cause is more often an absorption problem, diarrhoea, heavy alcohol use or medication.

Sports drinks and ready-made electrolyte drinks contain salts and often sugar, and whether they are needed depends on the situation. In everyday life or a short workout, water and normal food are enough. In a long, hot and strenuous effort, replacing salts can make sense, but drinking only plain water in large amounts can, on the contrary, dilute sodium.

Keeping electrolytes in balance and preventing problems

Keeping the balance is mostly about ordinary things. Drinking regularly, eating a varied diet and treating existing illnesses well usually keep electrolytes where they should be. For older adults the usual recommended fluid intake is 1.5 to 2 litres a day, and support from carers or relatives helps when the sense of thirst has weakened.

During a stomach bug, replacing fluids from the start helps to prevent dehydration. In hot weather it makes sense to dress lightly, take breaks and let the body adapt to the heat over 10 to 14 days before heavy exertion. A person who takes diuretics or has kidney or heart disease may have blood tests planned by a doctor to follow the levels.

Eating extra salt does not prevent low sodium. If the body is prone to holding on to water, drinking too much should be avoided, and the cause is worth working out with a doctor. Large amounts of liquorice are best limited, because it can lower potassium.

Older adults, small children and people with chronic illness are the most prone to dehydration. In them, vomiting, diarrhoea or fever can quickly unsettle fluid balance, so replacing fluids early is important. If drinking fails or the person gets worse, it is better not to wait long before contacting care. Acute kidney injury can also develop with dehydration, and its treatment begins in hospital with fluids.

When to see a doctor

Short stomach bugs can be followed at home when drinking works. Replacing fluids and salts, light eating and rest are then enough. The symptoms should be mild, and the person should be improving within a few days.

It is worth contacting a doctor if vomiting or diarrhoea lasts longer than two weeks, if fever rises above 38.5 degrees, or if drinking does not work. The same applies if urine stays dark for a long time or very little is passed, if muscle cramps and weakness keep coming back, or if someone who takes diuretics gets a stomach bug. For small children, older adults and people with long-term illness the threshold for seeking an assessment is lower.

Urgent help is needed if there is confusion, unusual drowsiness, seizures, fainting, severe muscle weakness or a feeling of an irregular heartbeat. Bloody stools, severe abdominal pain and dry skin in hot conditions are also reasons to go to emergency care. In a small baby, worrying signs are drowsiness, a sunken soft spot and no wet nappies. In an emergency, call the local emergency number.

How Dokport can help with a suspected electrolyte imbalance

If a stomach bug has drained your strength or you suspect that your electrolytes are out of balance, a remote doctor through Dokport can assess the situation quickly and easily by chat. The doctor asks about symptoms, drinking, illnesses and medicines, and judges whether it is something to follow at home or whether further tests are needed. This way the situation does not have to be left to guesswork.

When needed, the doctor directs you to blood tests, an in-person appointment or emergency care if the symptoms call for closer examination. The doctor decides independently what care the situation requires. Remote care is not suitable for serious symptoms such as confusion or seizures, which need immediate treatment in person.

Summary

Electrolytes, meaning sodium, potassium, calcium, magnesium and other salts, keep the muscles, the heart and the nervous system working. An imbalance most often arises from fluid loss, kidney disease or medicines, and in its mild form it is often without symptoms. A blood test shows the levels, and treatment depends on the cause: fluids and food are enough in a mild situation, while a severe one needs hospital care. Confusion, seizures and a feeling of an irregular heartbeat are signs that call for urgent care.