Electrolyte Test

Overview

An electrolyte test is usually a blood test that measures the levels of electrolytes in your body. Electrolytes are minerals in your body fluids that carry a tiny electric charge. The main ones are sodium, potassium, chloride, bicarbonate, calcium, magnesium and phosphate. They do important jobs: they keep the amount of water in your body balanced, help your muscles (including your heart) work properly, and help your nerves send signals. If your levels are too high or too low, you can feel unwell. The test tells your doctor whether your levels are in the normal range and whether anything needs to be checked or corrected.

Very common. Electrolyte tests are done millions of times a year in hospitals and GP surgeries, often as part of a routine check or when someone is unwell. Many people have one without even knowing the name of it.

Anyone can have an electrolyte test. It is more likely to be offered if you are in hospital, are feeling very sick or dehydrated, have a kidney, heart, liver or hormone condition, take certain prescribed medicines, or are having surgery. Babies and young children, athletes doing long or intense exercise, and older adults can be more likely to develop an imbalance, but the test itself is safe for everyone.

Symptoms

Common symptoms

• Often no symptoms at all — the imbalance is only found on a test
• Feeling very tired or low on energy
• Muscle weakness, aches or cramps
• Headache, feeling dizzy or light-headed
• Feeling thirsty more than usual
• Feeling sick or being sick
• Palpitations — being aware of your heartbeat, or a heartbeat that feels fast or uneven
• Confusion, poor concentration or feeling 'foggy'
• Swelling in the legs or ankles (linked to sodium and fluid balance)

Symptoms in children

• Being sleepier or floppier than usual, or harder to wake
• Refusing feeds or drinking much less than normal
• Being sick or having loose, watery poo (diarrhoea)
• Dry mouth, few tears when crying, or fewer wet nappies
• Sunken eyes or a sunken soft spot on the head in babies
• Irritability or unusual crying
• Muscle twitching or jerky movements — seek medical help quickly

Symptoms in older adults

• New confusion or memory problems, which can be the first sign
• Feeling weak, unsteady on your feet, or having a fall
• Feeling very tired or drowsy
• Dry mouth, thirst, or passing less urine than usual
• An irregular or racing heartbeat
• Swelling in the legs or ankles
• Feeling sick or going off food

Causes

Main causes

• Losing body fluids through vomiting, diarrhoea, heavy sweating, burns or high fever
• Not drinking enough fluids, or drinking very large amounts of water
• Kidney problems — the kidneys balance most electrolytes, so when they do not work well, levels can drift
• Some prescribed medicines, including water tablets (diuretics), laxatives, steroids and some heart or blood pressure medicines
• Hormone problems, such as thyroid or adrenal gland conditions, or diabetes and its treatment
• Heart failure or liver disease, which change how fluid and salts are balanced
• Receiving fluids through a drip (IV fluids) in hospital
• Poor diet, long periods of not eating, or an eating disorder
• Surgery, injury, or a long stay in intensive care

Risk factors

• Being in hospital or having recently had surgery
• Having kidney disease, diabetes, heart failure or liver disease
• Taking water tablets (diuretics) or other medicines that affect fluid balance
• Being older — thirst and kidney adjustment are less efficient with age
• Being very young, especially with vomiting, diarrhoea or poor feeding
• Long or intense exercise, especially in hot weather
• Alcohol misuse or recreational drug use
• An eating disorder, or long periods of restricted eating
• Severe morning sickness in pregnancy

When to see a doctor

See a doctor urgently if:

• You cannot keep fluids down because of vomiting, or you have had diarrhoea for more than a day or two
• You feel very dizzy, faint or unsteady when you stand
• You notice a racing, pounding or uneven heartbeat
• You have muscle cramps, twitching or weakness that is getting worse
• You feel unusually confused or drowsy
• A baby or young child is feeding poorly, has fewer wet nappies, or is much sleepier than usual

Book a routine appointment if:

• You feel tired, weak or thirsty for no clear reason
• You have been told before that your electrolyte levels were borderline
• You take water tablets (diuretics) or other medicines that need regular blood checks
• You have a long-term condition such as kidney disease, diabetes, heart failure or a hormone problem
• You are planning to start a very low-salt or 'detox' diet, or to take salt or potassium supplements

Diagnosis

Your doctor diagnoses an electrolyte imbalance by testing a sample of your blood, and sometimes a sample of your urine. The blood test is often called 'urea and electrolytes' or 'U&E'. It may be done alone or as part of a wider set of blood tests. If a result is unusual, your doctor may repeat the test, ask about what you have been eating, drinking and any medicines, and examine you. Sometimes an ECG (a heart tracing) is done, because potassium and calcium levels can affect the heartbeat.

Tests that may be done

• Blood test (often a 'urea and electrolytes' or U&E panel), taken with a small needle from a vein in your arm
• Urine test to see how well your kidneys are handling salts and water
• Other blood tests such as blood sugar, kidney function or hormone tests, depending on what the first results show
• An ECG (heart tracing) if your potassium or calcium level is unusual or you have heart symptoms
• A repeat test after treatment to make sure levels have returned to normal

What to expect at your appointment

It is a quick and simple test: a nurse or phlebotomist will clean your skin, put a small needle into a vein (often inside the elbow), and fill one or two small tubes. It takes a minute or two and feels like a short pinch. You can eat and drink as normal beforehand unless you are told otherwise. Results usually come back within a few hours in hospital and within a few days at a GP surgery. Your doctor will explain what the numbers mean for you — do not try to interpret them on your own from the internet.

Treatment

Treatment depends on which electrolyte is out of balance and why. The first step is usually to treat the cause — for example, easing vomiting and diarrhoea, adjusting a medicine that is affecting your levels, or managing a kidney or hormone condition. If your levels are only slightly out and you feel well, you may not need any treatment at all beyond a repeat test. If levels are further out, or you feel unwell, your doctor will replace what is missing and check that it works.

Self-care at home

• Keep sipping fluids if you have vomiting or diarrhoea — small, frequent sips are easier to keep down than large drinks
• An oral rehydration solution from a pharmacy can help replace salts and water during illness — ask your pharmacist which one suits you
• Avoid drinking very large amounts of plain water in a short space of time
• Do not take salt tablets, potassium supplements or 'electrolyte' sports products unless a healthcare professional has advised it
• Eat regular balanced meals — fruit, vegetables, dairy or dairy alternatives, beans, nuts and wholegrains all supply electrolytes naturally
• Bring an up-to-date list of your medicines, including anything you buy over the counter, to your appointment
• If you are taking a water tablet, do not stop it on your own — speak to your GP or pharmacist first

Medical treatments

Your healthcare team will treat the cause as well as the level. This may mean replacing lost salts and water by mouth, or through a drip into a vein if you cannot drink enough or the imbalance is more serious. Some people need a medicine adjusted or stopped, and occasionally a different medicine is started to help the body hold onto or get rid of a particular electrolyte. Hormone or kidney problems may need specialist care. You will usually have a repeat blood test to confirm things are back in range. Your team will tell you exactly what is being given and why — always ask if you are unsure.

When is surgery considered?

Surgery is not a treatment for an electrolyte imbalance itself. Occasionally a problem that causes an imbalance, such as a blockage in the bowel or a hormone-producing growth, may need an operation. Your surgical team would check and correct your electrolyte levels before any planned operation, because balanced levels make surgery safer.

Living with this condition

Most people do not need to 'live with' an electrolyte problem for long — once the cause is treated, levels usually return to normal. If you have a long-term condition that affects your levels, such as kidney disease or heart failure, you may have regular blood tests to keep an eye on things. Keeping a simple note of your test dates, results and any symptoms can make your appointments more useful.

Lifestyle tips

• Drink regularly through the day rather than large amounts all at once
• Take extra care in hot weather and during exercise — drink and rest sensibly
• Limit alcohol, which affects fluid balance and can lower some electrolyte levels
• Do not follow very restrictive 'detox', salt-free or water-only regimes without medical advice
• Keep taking prescribed medicines as directed and check before stopping anything
• Take extra care if you have a stomach bug — rehydrate early, especially in children and older adults

Diet and exercise

A varied, balanced diet supplies all the electrolytes you need for most people, so supplements are rarely necessary and can sometimes be harmful. Salty foods, processed foods and very low-salt diets can all shift sodium levels, so aim for ordinary balanced meals rather than extremes. If you exercise hard or for a long time, drink water and eat normally afterwards; sports drinks are only really useful for long, sweaty sessions and are not needed for everyday activity. If you have a kidney or heart condition, your team may give you specific advice about salt, potassium and fluid — follow that advice rather than general rules.

Mental health and emotional wellbeing

Being told your blood test is abnormal can be worrying, and feeling unwell with tiredness, cramps or a racing heartbeat can affect your mood and sleep. In rare cases, an electrolyte problem itself can cause confusion or low mood, which improves when the level is corrected. It is very reasonable to feel anxious while waiting for results. Write down your questions, take someone with you to appointments if you can, and tell your doctor if worry is affecting your sleep or daily life.

Prevention

Some causes cannot be prevented, but many imbalances can be avoided or caught early. Drinking enough fluid, eating a balanced diet, treating vomiting and diarrhoea promptly with fluids, and having recommended blood tests if you take medicines that affect salts and water all help. Never take salt or potassium supplements, or heavily restrict salt, without checking with a healthcare professional first.

Screening programmes

There is no general screening programme for electrolyte levels in healthy people. Blood tests are offered when they are useful — for example, before some operations, when you start or change certain medicines, or if you have a long-term condition that can affect your levels. Your GP will advise how often you need checking.

Complications

If left untreated

• Continued tiredness, weakness, cramps or dizziness
• An irregular or fast heartbeat, which can be serious if it is not treated
• Severe muscle weakness, or muscles that will not work properly
• Confusion, drowsiness or a fall, especially in older adults
• A fit or seizure when levels are very low or very high
• Kidney strain if dehydration or a kidney problem is not managed
• Very rarely, a severe imbalance can become life-threatening — this is why heavy vomiting, diarrhoea or a racing heartbeat should not be ignored

Long-term outlook

The outlook is usually very good. Most electrolyte imbalances found on a test are mild and put right quickly once the cause is known, often simply by treating the illness causing it or adjusting a medicine. Some people have a long-term condition that needs ongoing checks, and with regular monitoring and good hydration the vast majority stay well and get on with normal life.

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