The short answer
E-liquid is the refill or prefilled formulation that a compatible vape heats into an aerosol. PG/VG ratio, nicotine formulation, nicotine concentration, bottle format, and flavour are separate decisions. No single liquid suits every device, no mg/ml label converts exactly into cigarettes, and neither price nor an MHRA listing proves that one bottle is harmless.
For nicotine products sold to consumers, current UK rules include a maximum nicotine concentration of 20mg/ml, a maximum refill-container size of 10ml, ingredient restrictions, warnings, child-resistant and tamper-evident packaging, and publication of a notification before sale. Notification is a compliance requirement, not medicinal approval. An adult who smokes can use a suitable regulated vape to switch completely, while children and people who do not smoke should not vape.
Key points
- Read PG/VG ratio, nicotine formulation, concentration, bottle format, and flavour separately.
- Device and coil instructions decide liquid compatibility; pod, MTL, or sub-ohm alone is not precise enough.
- Nicotine delivery varies with liquid, device, power, experience, and puffing, so mg/ml is not a cigarette converter.
- MHRA publication is required for legal supply of nicotine products but is not medicinal approval or proof of zero risk.
- Price, colour, natural wording, food-grade wording, and flavour name do not create a reliable safety ranking.
Most e-liquid confusion comes from comparing labels that answer different questions. A bottle can be 50/50 and use nicotine salt. A shortfill can be VG-led but shortfill describes the partially filled bottle, not a nicotine chemistry. A 10ml refill can contain freebase nicotine, salt nicotine, or no nicotine.
This FAQ answers the broad questions directly, then links to the deeper calculation or health guide when a short answer would be misleading. Start with the five-part label below. If you are making a purchase decision, the full e-liquid selection guide gives the complete sequence.
Five e-liquid labels that answer different questions
| Comparison point | What it describes | Example | Question it cannot answer alone |
|---|---|---|---|
| PG/VG ratio | Relative carrier proportions and resulting viscosity pattern | 50/50 or 70VG/30PG | Nicotine type, strength, bottle format, or exact compatibility |
| Nicotine formulation | Salt, freebase, or nicotine-free formulation | Nicotine salt | How much nicotine is present or absorbed |
| Concentration | Milligrams of nicotine per millilitre of liquid | 10mg/ml or 1 percent | Dose per draw, daily absorption, or cigarette equivalent |
| Bottle or pod format | How the liquid is supplied and whether it needs filling or mixing | 10ml refill, shortfill, or prefilled pod | Whether its ratio and strength suit your exact hardware |
| Flavour description | The sensory profile the producer intends to communicate | Mint, berry, dessert, or tobacco | A full ingredient list, personal taste result, or safety grade |
Important context: A single product can carry all five labels at once. Compare like with like before deciding that one category is better.
What e-liquid is, and what the device changes
E-liquid is a formulation intended for a compatible vaping device. It commonly contains PG, VG, flavourings, and sometimes nicotine, but that familiar list is not a universal four-ingredient recipe. Water, ethanol, acids used in salt formulations, sweeteners, cooling agents, or other permitted constituents may be present.
The device brings the liquid to a wick and heats it at the coil. That produces an aerosol rather than smoke or simple water vapour. Liquid composition, power, airflow, coil condition, device materials, and puffing can all affect the aerosol. For a full explanation, read what is in e-liquid and aerosol.
This is why “can it physically fit?” is the wrong compatibility test. A liquid can enter a tank and still be too viscous for its wicking ports, too thin for its seals and airflow design, or an unsuitable nicotine concentration for the device output.
Run these checks before filling a device
Identify the exact device, pod, and coil
Read the installed resistance and official compatibility guidance. Similar-looking pods can use different liquid and power ranges.
Match the supported PG/VG range
Use the producer instruction for viscosity. Small wicking ports commonly suit balanced liquid, while larger high-output coils commonly accept thicker VG-led liquid, but neither pattern is universal.
Choose nicotine with the whole setup in mind
Concentration, salt or freebase formulation, device output, puffing, dependence, and smoking goal interact. Avoid a rigid cigarettes-per-day chart.
Check the exact product record and packaging
For nicotine products, match the relevant MHRA-published identity and inspect the seal, warning, ingredients, concentration, volume, batch, and responsible supplier.
Follow filling or priming instructions
Use the method and wait time for that pod or coil. Do not assume one universal five-minute rule, and never put e-liquid into a port intended for airflow or charging.
The nicotine label is concentration, not personal dose
OHID found that nicotine exposure from vaping varies with concentration, salt or freebase formulation, device type, user experience, and puffing. Some people compensate for lower concentration with longer, larger, or more frequent puffs. Experienced users can reach nicotine exposure comparable with smoking over longer use even when the short-session delivery pattern differs.
That evidence rules out a reliable universal conversion from one millilitre, one pod, or one puff to a fixed cigarette count. It also rules out the claim that salt nicotine always behaves identically or that lower mg/ml always means lower daily exposure. The useful cessation outcome is controlled withdrawal and zero cigarettes without unsuitable effects.
OHID 2022 nicotine evidence summaryEvidence checked 2026-08-06
Limitation: Population and laboratory evidence cannot prescribe the right nicotine concentration or predict the absorbed dose for one person and setup.
UK regulation is a baseline, not a safety league table
| Comparison point | What to verify | What it supports | What it does not prove |
|---|---|---|---|
| MHRA-published notification | Exact nicotine product, flavour, and concentration on the relevant list | A required market-compliance step has been published | Medicinal approval, zero risk, or authenticity of one physical unit |
| Nicotine limits | No more than 20mg/ml and no more than 10ml in a consumer refill container | A visibly conflicting presentation should not be supplied | The allowed maximum suits every adult or device |
| Packaging and ingredient rules | Warnings, child resistance, tamper evidence, information, and specified ingredient restrictions | Minimum consumer and product protections for the regulated category | Every flavour has the same inhalation evidence or every bottle passed identical tests |
Important context: MHRA explicitly says its consumer-product role does not involve approving these products. Nicotine-free products do not use the same TRPR notification route.
Dates, storage, and colour need product-specific judgement
Flavour compounds and nicotine can change over time, and storage conditions matter. A 2025 study tracked 20 flavouring chemicals and commercial liquids for 24 months. Its reference solutions stored at room temperature with ambient light were the least stable, while reduced light and colder storage delayed degradation for some compounds.
That finding supports following the product direction to keep a bottle closed and away from heat and direct light. It does not justify freezing every retail liquid, extending a printed date, or assigning one opened-bottle lifespan. Formulations, containers, seals, and directions differ.
Darkening can occur through oxidation and interactions in the formulation, but colour alone does not reveal the full chemistry or decide safety. Check the date, storage history, seal, smell, consistency, labelling, and producer advice together. Do not use a bottle with suspected contamination, damaged packaging, an unexplained change that concerns you, or an identity you cannot verify.
Use e-liquid advice for the goal you actually have
If you smoke and want to switch completely
Choose a simple compatible setup with enough nicotine to control withdrawal and get support
The NHS benefit is tied to replacing cigarettes, while poor compatibility or inadequate craving control can undermine the attempt.
Watch for: A retailer guide cannot prescribe nicotine. A stop-smoking adviser can consider dependence, previous attempts, device, and response.
If you already vape and want to change format or draw style
Reassess ratio and nicotine whenever output changes
Moving between MTL, RDL, and DTL changes airflow, aerosol per draw, liquid use, and the nicotine context.
Watch for: Do not carry a high concentration into a high-output setup just because both products are sold separately. Use the <a href="/vape-guide/vape/understanding-the-differences-between-mtl-and-dtl-vaping/">MTL, RDL, and DTL guide</a>.
If you do not smoke
Do not start vaping
The lower-risk comparison applies to replacing smoking. Starting adds aerosol exposure and may add nicotine dependence.
Watch for: Nicotine-free liquid does not make inhalation harmless.
If you are pregnant and want to stop smoking
Speak to a GP or stop-smoking professional about recommended options
The NHS recommends licensed nicotine replacement products in pregnancy and individual clinical advice.
Watch for: Do not use a retail strength guide as pregnancy care.
17 common e-liquid questions answered
Can I put any e-liquid in any vape?
No. Match the exact pod or coil’s supported viscosity and power, then consider nicotine concentration and formulation. A liquid can physically enter a tank yet wick poorly, leak, or create an unsuitable nicotine-output combination.
Is 50/50 the same as nicotine salt?
No. 50/50 describes the PG/VG ratio. Nicotine salt describes the nicotine formulation. A 50/50 liquid can use salt, freebase, or no nicotine.
What is a shortfill?
It is normally a larger bottle of nicotine-free e-liquid with space left for an optional compatible nicotine shot. Shortfill is a bottle format, not a PG/VG ratio. Calculate any final nicotine concentration from total nicotine divided by final volume.
Are nicotine salts better than freebase nicotine?
Neither is universally better. Salt formulation, acid, pH, concentration, device, and puffing affect sensation and delivery. Choose from the smoking goal, compatible hardware, and personal response rather than a speed or smoothness promise.
What nicotine strength should I use?
No online chart can prescribe it from cigarettes per day alone. Dependence, time to first cigarette, device output, formulation, puffing, previous attempts, cravings, and side effects matter. An adult quitting smoking can ask a stop-smoking adviser.
How many cigarettes is one bottle or pod?
There is no exact conversion. A label can show total nicotine in the liquid, but device transfer, puffing, frequency, and absorption vary. Use the nicotine comparison guide for the maths and its limits.
Which e-liquid is safest?
There is no evidence-based safest flavour, ratio, or price tier. A verifiable regulated product used in compatible hardware reduces avoidable uncertainty, but vaping remains not risk-free. For someone who does not smoke, not vaping is lower risk.
Does MHRA listing mean an e-liquid is approved?
No. MHRA says its consumer-product role does not involve approving the products. Publication shows the notification needed for legal supply, subject to compliance and enforcement. It is not a medicine licence or authentication of one unit.
Is expensive e-liquid safer or better?
Price does not establish safety, composition, compatibility, or taste quality. It can reflect brand, bottle format, distribution, ingredients, tax, or positioning. Compare verifiable product facts rather than treating price as a laboratory result.
Does e-liquid expire?
It can change with time and storage. Follow the printed date and producer directions. Keep it closed and away from heat and direct light. Do not extend the date from a generic claim that opened liquid lasts a fixed number of months.
Why has my e-liquid turned brown?
Oxidation and formulation interactions can change colour, but colour alone cannot identify all chemistry or establish safety. Check the date, storage, seal, smell, consistency, batch, and producer advice. Stop if contamination or an unexplained change concerns you.
Can I mix two e-liquids?
Mixing compatible regulated liquids changes the final nicotine concentration, PG/VG ratio, flavour, and potentially device suitability. Calculate the result first. Do not add food flavouring, oil, household ingredients, or unregulated nicotine concentrate.
Does one nicotine shot always make a shortfill 3mg/ml?
No. Multiply shot concentration by shot volume, then divide by final mixed volume. One 10ml shot at 18mg/ml added to 50ml of zero-nicotine liquid makes 60ml at 3mg/ml. Different inputs give a different result.
Why does my liquid suddenly taste weak or burnt?
Check liquid level, coil or pod condition, supported power, airflow, compatibility, and bottle condition. If food or everyday smells also changed, use the lost vape flavour guide and consider the health pathway.
What should I do if e-liquid is swallowed?
Get medical advice immediately under current NHS poisoning guidance. Use 999 or A&E for the listed emergencies and NHS 111 if unsure whether the exposure is harmful. Do not induce vomiting or give food or drink unless directed.
Can e-liquid cause side effects?
The NHS lists coughing, dry mouth and throat, irritation, shortness of breath, and headaches among common reported vaping side effects. Stop an unsuitable product, seek advice appropriate to the symptom, and report suspected adverse effects through MHRA Yellow Card.
Can children or non-smokers use nicotine-free e-liquid?
They should not start vaping. Nicotine-free removes nicotine from the declared formulation, not aerosol exposure or every risk. Vape products are not recommended for children, young people, or people who do not smoke.
Live products, prices and stock
This article explains the question or review. Use the linked shop pages for current product options, prices and availability.
Related reading
Sources and verification
- Using e-cigarettes to stop smokingNHSPublished or updated: 15 July 2026Checked: 6 August 2026
Supports: Typical liquid constituents, aerosol, smoking comparison, nicotine, pregnancy, non-smoker advice, and safety reporting.
- Vaping to quit smokingNHS Better HealthChecked: 6 August 2026
Supports: Nicotine and product choice for cessation, common side effects, support, and Yellow Card reporting.
- E-cigarettes: regulations for consumer productsMedicines and Healthcare products Regulatory AgencyPublished or updated: 16 August 2024Checked: 6 August 2026
Supports: Nicotine concentration, refill-container and tank limits, ingredient restrictions, packaging, warning, and notification requirements.
- More information about the MHRAMedicines and Healthcare products Regulatory AgencyChecked: 6 August 2026
Supports: Explicit distinction between consumer product notification and approval, plus the different position for nicotine-free products.
- Nicotine vaping in England: 2022 evidence update summaryOffice for Health Improvement and DisparitiesPublished or updated: 29 September 2022Checked: 6 August 2026
Supports: Variability in nicotine delivery, salts versus freebase, device and puffing effects, compensatory use, dependency, flavours, and exposure.
- Advice on ingredients in nicotine-containing e-liquidsMedicines and Healthcare products Regulatory AgencyPublished or updated: 16 August 2024Checked: 6 August 2026
Supports: Ingredient and emissions safety responsibilities, toxicology requirements, prohibited substances, and why food-use status does not establish safe use in an e-cigarette.
- PoisoningNHSPublished or updated: 12 June 2025Checked: 6 August 2026
Supports: Immediate action after suspected harmful ingestion, contact, or inhalation and instructions not to induce vomiting.
- Stability of flavoring chemicals in e-cigarette liquids over 24 monthsACS OmegaPublished or updated: 8 April 2025Checked: 6 August 2026
Supports: Product-ageing study on flavour chemical stability under different light and temperature conditions.
- Vapes FAQVaporessoChecked: 6 August 2026
Supports: Manufacturer troubleshooting for priming, liquid supply, supported power, old filled pods, and burnt taste.
Editorial record
- Last reviewed
- 6 August 2026
- Next review due
- 10 November 2026
What changed
Rebuilt the FAQ around separate label decisions, current UK rules, nicotine-delivery uncertainty, device compatibility, storage evidence, poisoning action, and cessation boundaries. Removed product picks, universal four-ingredient language, safety-by-price claims, exact cigarette matching, and fixed coil-resistance prescriptions.
Disclosure
Vape Forest sells e-liquids and compatible hardware and benefits from purchases in these categories. This FAQ removes unsupported product rankings and does not prescribe nicotine, certify a liquid, or replace manufacturer and healthcare instructions.
