Dehydration and intravenous (IV) fluid therapy (Assessment of dehydration and intravenous fluid therapy)
When dehydration or fluid loss is treated by giving fluids directly into a vein through a drip, why it is sometimes needed, and why 'wellness' vitamin drips are a different and questionable thing.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- IV fluids replace fluid through a drip when someone is too dehydrated or unwell to drink enough — given for a clinical reason in a monitored setting.
- They treat the lack of fluid but not the cause; an infection, kidney problem or ongoing loss still needs treating in its own right.
- The type, amount and speed of fluid are chosen and monitored carefully, because too much or the wrong balance of salts can cause harm.
- 'Wellness', vitamin, immunity or hangover drips sold cosmetically are not evidence-based and carry real risks — a marketing red flag, not medicine.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your specialist will give you advice for your situation.
Quickly restores fluid when someone is too unwell or dehydrated to drink enough
Cosmetic 'wellness', vitamin or hangover drips are not appropriate medical treatment for well people and are not endorsed here.
Fluid is given through the cannula while your pulse, blood pressure, urine output and blood tests are monitored to check your response.
Clear advice on caring for the cannula site and what signs of infection to watch for.
Fluid is given through the cannula while your pulse, blood pressure, urine output and blood tests are monitored to...
Many people start to feel better as fluid is replaced and the circulation improves, though this depends on the...
Once you can drink enough and are improving, the drip is stopped and the cannula removed. You move back to fluids...
The puncture site is pressed and may bruise. Any redness, swelling, pain or pus at the site should be reported.
What is intravenous fluid therapy for dehydration?
Intravenous (IV) fluid therapy means giving fluids straight into a vein through a thin tube called a cannula. It is used when someone is dehydrated or has lost fluid and cannot replace it quickly enough by drinking — for example with severe vomiting, diarrhoea, infection, or when they are too unwell to drink.
It is a medical treatment given for a clinical reason, after a doctor has assessed how dehydrated you are by checking your pulse, blood pressure, how your circulation is working, and usually blood tests. The type and amount of fluid, and how fast it is given, are chosen deliberately and monitored, because giving too much, too little, or the wrong balance of salts can cause harm.
IV fluids treat the lack of fluid, but they do not on their own treat the cause. If dehydration is from an infection, the infection still needs treating; if from a kidney problem, that needs managing too.
This is very different from 'IV vitamin' or 'hydration' drips sold cosmetically for energy, hangovers, immunity or beauty. Those are not supported by good evidence, are not without risk, and are a marketing red flag rather than a treatment for a medical problem. Most well people who feel run down do not need a drip, and can rehydrate safely by mouth.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Options at a glance
These are the main approaches described in this guide. The right option depends on the diagnosis, your goals and what your clinician thinks is safe.
Resuscitation fluids
Given quickly when someone is seriously low on fluid and their circulation is struggling (for example in severe infection or heavy fluid loss). Salt-containing fluids are...
Replacement and maintenance fluids
Used to make up an existing fluid or salt deficit and to cover ongoing needs in someone who cannot drink enough. The amount and type are matched to blood tests and fluid...
Oral and other routes first
Where possible, fluids by mouth (or oral rehydration solutions) are preferred, because they are safer and avoid a cannula. IV is reserved for when drinking is not enough or...
Cosmetic 'wellness' or vitamin drips
IV fluids, sometimes with added vitamins, sold privately for energy, hydration, immunity, beauty or hangovers. These are not evidence-based for those claims, are largely...
Preparing for your treatment
- If you are seriously unwell — drowsy, not passing urine, breathless, with a racing heart, or unable to keep fluids down — seek urgent medical help; do not wait for a routine drip appointment.
- Tell the team about heart failure, kidney problems or any condition where extra fluid could be harmful.
- Bring a list of your medicines, including water tablets (diuretics) and blood-pressure medicines.
- Describe your recent fluid losses — vomiting, diarrhoea, fever, sweating — and how much you have managed to drink.
- Mention any allergies and any previous problems with cannulas or infusions.
- Expect blood tests before and during treatment to guide the type and amount of fluid.
What happens
A doctor or acute physician assesses how dehydrated you are — checking pulse, blood pressure, how your circulation is working, and usually taking blood tests for your salts and kidney function. They decide whether you genuinely need IV fluids or whether drinking is enough.
If IV fluids are needed, a cannula is placed in a vein, usually in the back of the hand or the arm. The chosen fluid is given through it, sometimes quickly if you are very unwell, sometimes slowly over hours. You are monitored — pulse, blood pressure, urine output and repeat blood tests — to check you are responding and not being given too much.
Throughout, the team also treats the cause of the dehydration, whether that is an infection, a stomach upset, a kidney problem or something else. Once you can drink enough and are improving, the drip is stopped.
Is this treatment right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- Cosmetic 'wellness', vitamin or hangover drips are not appropriate medical treatment for well people and are not endorsed here.
- IV fluids are usually unnecessary for mild dehydration that can be treated by drinking or with oral rehydration solutions.
- Extra fluid can be harmful in heart failure, advanced kidney disease and some other conditions, where it must be given with great care or avoided.
- An outpatient drip is the wrong setting for someone who is seriously unwell and needs hospital-level assessment and monitoring.
Delay or rearrange if…
- There are signs of serious illness needing emergency care — do not delay, seek urgent help.
- The cause of fluid loss has not been assessed and could be a serious problem needing other treatment.
- Blood tests of salts and kidney function, which guide the fluid choice, are not available.
- There is uncertainty about heart or kidney conditions that make extra fluid risky.
Alternatives to discuss
- Oral fluids or oral rehydration solutions, which are safer and avoid a cannula.
- Treating the underlying cause (for example anti-sickness treatment so the person can drink).
- Subcutaneous fluids in selected situations under medical guidance.
- Doing nothing beyond reassurance and oral fluids in well people who simply feel tired.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- Quickly restores fluid when someone is too unwell or dehydrated to drink enough
- Supports the circulation in serious illness while the cause is treated
- Allows salts (electrolytes) to be corrected in a controlled way
- Buys time and stability while infection or another cause is managed
- Can be stepped down to drinking as the person recovers
Risks & complications
- Discomfort, bruising or a small bleed where the cannula is placed
- The cannula stops working and needs re-siting
- Swelling or leakage of fluid into the tissue around the cannula
- Needing repeated blood tests to guide treatment
- Too much fluid, causing swelling or fluid on the lungs, especially in heart or kidney problems
- Salt imbalances if the wrong fluid or rate is used
- Inflammation of the vein (phlebitis) at the cannula site
- A local skin or soft-tissue infection at the cannula site
- A bloodstream infection from the cannula
- A serious allergic reaction to a fluid or additive
- Harm from rapid correction of certain salt problems
- Blood clot related to the cannula
The biggest risks are giving fluid to someone who does not need it, and giving the wrong amount or balance to someone who does — both can cause harm, especially in heart or kidney disease. The other key point is that fluids do not treat the cause. For cosmetic 'wellness' drips, the risks of a cannula and infusion are real while the claimed benefits are not evidence-based, so the risk-benefit balance is poor. Ask why you need IV rather than oral fluids, what is being given and why, and how you will be monitored.
Published figures to discuss
Reliable single percentages are hard to give because risk depends on why fluids are given, how much, how fast, the person's heart and kidney health, and how carefully they are monitored. The harms of unnecessary or poorly monitored fluids are well recognised even where exact rates are not.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Fluid overload | Higher in heart, kidney or liver disease | Breathlessness, swelling or low oxygen after IV fluids needs urgent review. | Guide sourcesClinical context |
| Electrolyte disturbance | Fluid- and patient-dependent | NICE IV fluid guidance emphasises checking sodium, potassium, kidney function and ongoing losses. | NICE CG174 — Intravenous fluid therapy in adults in hospital (recommendations)nice.org.ukSource-linked context |
| Cannula infection, infiltration or phlebitis | Recognised | Pain, swelling, redness or leakage around the cannula should be reported. | JAMA Internal Medicine — State policies and facility practices of IV hydration spas in the USjamanetwork.comSource-linked context |
| Underlying cause of dehydration missed | Important | Sepsis, diabetic ketoacidosis, bowel obstruction, bleeding or adrenal crisis may present with dehydration. | JAMA Internal Medicine — State policies and facility practices of IV hydration spas in the USjamanetwork.comSource-linked context |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is no separate recovery from the drip itself. How quickly you feel better depends on the underlying cause. The cannula site usually settles within a day or two of removal.
- A small bruise or tender spot where the cannula was
- Passing more urine as you rehydrate
- Feeling steadily better as fluid is replaced and the cause is treated
- Mild thirst easing once fluids are replaced
Aftercare
- Keep drinking to the level advised once the drip is stopped, unless told to limit fluids.
- Keep the cannula site clean and watch it for redness, swelling, pain or discharge.
- Continue any treatment for the underlying cause, such as antibiotics for an infection.
- Restart any paused medicines, such as water tablets, only when your clinician advises.
- Attend any follow-up blood tests to check your salts and kidney function.
- Report a fever, increasing pain or redness at the cannula site, or feeling more unwell.
- Seek urgent help if you become breathless, swollen, or cannot keep fluids down again.
- A clear note of recent fluid losses and how much you can drink
- An up-to-date list of medicines, especially water tablets and heart medicines
- Details of heart failure, kidney disease or fluid-sensitive conditions
- A record of any allergies or past infusion problems
- A written copy of what was given and the plan for the underlying cause
- Instructions on caring for the cannula site and what to watch for
- The contact number for questions or worsening symptoms
Scars and how they heal
There are no surgical wounds. A cannula is placed in a vein, usually in the back of the hand or the forearm, leaving a small puncture mark and sometimes a bruise that fades over days. Occasionally the vein can become inflamed (a tender, red, firm line), which usually settles. A lasting mark is uncommon.
⚠ Get urgent help if…
- Breathlessness or difficulty breathing during or after fluids — call 999
- Sudden swelling of the face, lips or throat, or a widespread rash — call 999 (possible allergic reaction)
- Spreading redness, severe pain, swelling or pus at the cannula site — seek urgent help
- A fever or feeling shivery and very unwell after a drip — seek urgent help
- Passing very little urine, drowsiness or confusion — seek urgent help
- A racing, slow or irregular heartbeat — seek urgent help
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your specialist gives you.
Results & realistic expectations
When IV fluids are used appropriately, the result is a person whose fluid state and circulation are restored while the cause of their dehydration is treated. Improvement is judged by your pulse, blood pressure, urine output and blood tests, not just by how you feel.
Fluids alone do not prove the underlying problem is solved. A drip can stabilise someone who still needs antibiotics, kidney care or other treatment. For cosmetic 'wellness' drips, any sense of feeling better is generally short-lived and no better than drinking fluids, and is not a meaningful health result.
Rehydration lasts as long as the cause is controlled and you keep up your fluids. If the underlying problem continues — ongoing vomiting, infection or kidney issues — dehydration can return and further treatment may be needed. There is no lasting benefit to repeated cosmetic drips in well people.
Related tests, treatments or support
IV fluids are usually combined with treatment of the cause — for example intravenous antibiotic therapy for a serious infection, or management of acute kidney injury. Electrolyte disturbances are often corrected at the same time, using the fluids and additives chosen for your blood results.
Follow-up & long-term care
Follow-up is mainly about the underlying cause: repeat blood tests to check salts and kidney function, a plan to restart any paused medicines, and review of the condition that led to dehydration. You should be told what to watch for at the cannula site and when to seek help.
- Keep up oral fluids to the level advised once you are better
- Attend follow-up blood tests to confirm salts and kidney function have settled
- Manage the underlying condition that caused the dehydration
- Watch the cannula site until it has fully settled
Repeat, follow-on and what comes next
- The fluid plan is adjusted as blood tests and the response change.
- A cannula may need re-siting if it stops working or the vein becomes inflamed.
- Fluids may need to be slowed or stopped if there are signs of too much fluid.
- Dehydration can recur if the underlying cause is not controlled.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- Clear advice on caring for the cannula site and what signs of infection to watch for.
- A plan to treat and follow up the underlying cause, not just the fluid loss.
- Repeat blood tests where needed to confirm salts and kidney function have settled.
- A named contact and clear warning signs that mean seeking urgent help.
- Honest advice that well people rarely need a drip and can rehydrate safely by mouth.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- The assessment of fluid state and the blood tests needed to guide treatment
- The setting and monitoring required (a sicker person needs closer monitoring)
- The type and amount of fluid and any additives
- Treatment of the underlying cause alongside the fluids
- Repeat blood tests and follow-up
- Whether admission is needed if outpatient treatment is not safe
- The assessing clinician's fee and appointment length
- The cannula, fluids and any additives
- Monitoring and blood tests before and during treatment
- Treatment of the underlying cause, if relevant
- What happens, and what it costs, if you need admission or further care
- Follow-up and repeat blood tests
- A clear statement that genuinely unwell people will be redirected to appropriate medical care
On the NHS? IV fluids are given on the NHS whenever they are clinically needed, in a monitored setting. Private 'wellness', vitamin or hydration drips marketed to well people are a different thing: they are not evidence-based and are not a substitute for medical assessment when someone is genuinely unwell.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Selling a drip as a treatment or pick-me-up without assessing whether it is needed at all.
- Not explaining that fluids do not treat the underlying cause.
- Implying vitamin or 'wellness' drips have proven health benefits.
- Not warning about cannula-site infection, vein inflammation and fluid overload.
- Not arranging the blood tests and monitoring that safe IV fluid therapy requires.
Marketing red flags
- IV vitamin, immunity, energy, beauty or hangover drips promoted as health treatments — not evidence-based and not without risks.
- Drips sold in salons, gyms or pop-ups without proper medical assessment or monitoring.
- Claims that a drip 'detoxes', 'boosts immunity' or 'rehydrates better than water' for well people.
- Bundles or memberships encouraging repeated infusions with no medical indication.
Choosing a specialist safely
- Check the specialist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good specialist will welcome every one of these.
- Why do I need IV fluids rather than drinking fluids?
- What fluid are you giving me, how much, and how fast?
- How will you monitor me to make sure I am not getting too much?
- What is being done to treat the cause of my dehydration?
- Do any of my conditions or medicines make extra fluid risky for me?
- When can I switch back to drinking, and when will the cannula come out?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the specialist who carries out my treatment, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this treatment not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
Do I need a drip, or can I just drink more?
Are 'wellness', vitamin or hangover drips worth it?
Is having a drip dangerous?
Will a drip cure my illness?
Why do I keep needing blood tests during treatment?
Can I have IV fluids privately if I just feel run down?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: NICE CG174 — Intravenous fluid therapy in adults in hospital (recommendations) NICE CG174 — key priorities for implementation NHS — Dehydration JAMA Internal Medicine — State policies and facility practices of IV hydration spas in the US JAMA — IV hydration spas: are they safe? To IV or not to IV: the science behind intravenous vitamin therapy (PMC)
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
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