Vape liquid, how to read the bottle before you buy

A 10ml bottle of e-liquid carries more useful information than most product pages. Ratio, nicotine strength, size, warning, batch number, a folded leaflet in the box, a calibrated nozzle, and each of them answers a specific rule. Yet vape liquid is often picked by flavour name alone, and the mistake only shows at the first refill. The real question is the order in which to read the bottle, and what each line on it actually changes for you and your kit.

The right vape liquid comes down to two reads of the bottle

Good vape liquid is chosen in two passes over the bottle. The first, on the front, sets the PG/VG ratio against the resistance of your coil and the nicotine strength against the way you vape. The second, on the back, the cap and inside the box, confirms that the bottle meets the rules for sale in the UK.

If the first read fails, the liquid will not suit your kit, whatever the flavour. If the second fails, put the bottle back. A missing warning, a warning not worded as UK law requires or a nicotine bottle larger than 10ml all point to a product outside British rules.

Front of the bottle, what ratio, strength and size mean for your kit

The front panel holds the details that change from one bottle to the next within the same range. This is where compatibility with your pod or tank is decided, well before flavour enters the picture.

PG/VG ratio and your coil

The ratio is written as two numbers, the first for propylene glycol (PG), the second for vegetable glycerine (VG). PG keeps the liquid thin, VG thickens it. A coil feeds itself by drawing liquid through its wick, and a liquid too thick for it leaves the coil running dry.

Makers therefore publish the coil resistance at which to switch from one ratio to another. These thresholds differ between brands and appear on their product pages, as our close read of Alfaliquid’s Ice Rocket shows with one flavour sold in two ratios.

Nicotine strength and its form

Strength is given in milligrams per millilitre. A 10ml bottle at 6mg/ml therefore holds 60mg of nicotine in total. In the UK, no nicotine e-liquid on sale may exceed 20mg/ml, which caps the top of every range.

The form of nicotine is part of the recipe. “Nic salts” refers to a different chemical form from the so-called freebase nicotine, and strength reads in mg/ml in both cases. Two bottles at the same strength, one salts and one freebase, remain two different products, and the choice between them is made on the label, not on the flavour.

Bottle size, 10ml at most once nicotine is involved

Size is not just a format preference. The Tobacco and Related Products Regulations 2016 limit nicotine-containing refill bottles to 10ml, tanks to 2ml and strength to 20mg/ml. Any larger bottle is sold without nicotine, as a shortfill.

That rule explains the whole shortfill format, where you add nicotine shots yourself. Its bottle reads differently, by comparing the volume of liquid with the real capacity of the bottle.

Back of the bottle, the wording UK law requires

The rest of the label follows fixed rules that apply to every brand. These lines look administrative, yet each one tells the buyer something concrete, as long as you know what it proves and what it does not.

The nicotine warning, sign of a bottle made for the UK

Every nicotine bottle must carry the text “This product contains nicotine which is a highly addictive substance”. It appears on both the front and back surfaces, covers 30% of each, and is printed in black Helvetica bold on a white background.

A bottle where that warning is missing, cut short or printed in another language was not prepared for sale in Britain. It is the fastest check on the whole bottle.

Ingredients, in order of weight

The ingredients list is compulsory and runs in descending order of weight. The first name is the heaviest component of the mix, not necessarily the largest by volume. Vegetable glycerine is denser than propylene glycol (1.261 against 1.036 g/cm³ at 20 °C, according to PubChem), so a 50/50 liquid by volume lists it first.

A bottle sold as VG-rich that lists propylene glycol first deserves a second look, since both statements cannot be right at the same time.

Batch number and the MHRA listing

The batch number appears on each unit, alongside the nicotine content and the ingredients list. It lets the maker trace the exact production run, which makes it the first detail to quote if you contact them.

The Medicines and Healthcare products Regulatory Agency (MHRA) publishes the list of notified products, and a nicotine e-liquid may not legally be supplied until its notification appears there. The agency also points out that being listed does not by itself confirm that the label meets UK requirements.

Cap and nozzle, the part of the label nobody reads

What the bottle says through its shape matters as much as its printed text. Nicotine bottles must be tamper-evident, fitted with a safety closure, and protected against breakage and leakage, under the same 2016 regulations.

Refilling follows a precise design rule. A nozzle bottle needs a securely attached nozzle at least 9mm long, narrower than the tank opening, releasing no more than 20 drops per minute when held upright at between 15 and 25 °C.

In practice, that nozzle decides how easily you refill. It has to fit the filling port of your pod or tank, and the instructions supplied with the bottle state the compatible dimensions. A tamper seal already broken at the point of sale means an opened bottle, which belongs back with the seller.

The leaflet folded inside the box

Every nicotine unit packet must contain a leaflet. It covers instructions for use and storage, the maker’s or importer’s contact details and the warnings set by the regulations.

It is the only document that explains, for this exact bottle, how to store it. Binning it with the box means losing the one storage instruction written for that liquid.

Every vape liquid label line matched to your kit

The table follows the order in which the bottle presents itself in your hand. For each line, the last column says what it decides, for your kit or for your purchase.

Label line	Where to find it	What it decides
PG/VG ratio	Front	The coil type, based on the maker’s thresholds
Strength in mg/ml	Front	How strong the liquid is, 20mg/ml at most
Salts or freebase	Front or product name	The form of nicotine, not to be swapped
Size	Front	10ml at most for a nicotine bottle
Nicotine warning	Front and back	A bottle prepared for the UK market
Ingredients	Back or side	The heaviest component, by weight
Batch and date	Label or box	Traceability and a storage reference
Nozzle and cap	Top of the bottle	Refilling, and whether the bottle is intact
Leaflet	Inside the box	Storage instructions, the maker’s contact

FAQ

These five questions come up often in front of a shelf of bottles. The sections above do not settle them directly, so here are short answers, each based on what the bottle or its box lets you check.

Which e-liquids should you avoid when reading the label?

Skip bottles whose label or product page gives neither ratio nor strength, and any sold loose without a box or leaflet. Without that information you cannot match the liquid to your kit or reach the maker if something goes wrong.

Is there a best brand of vape liquid?

La Fiole Bleue does not rank brands. The most useful marker is transparency, meaning a brand that publishes ratio, strength, ingredients and contact details for every product. A voluntary certification can add to that, without replacing a proper read of the bottle.

Why does the same flavour come in several ratios?

To cover different families of kit. One recipe can be offered in a thinner ratio for higher-resistance coils and a VG-richer ratio for lower ones. The flavour stays the same, only compatibility changes.

What if the label is damaged or unreadable?

Keep the box. The compulsory wording also appears on the outer packaging, and the leaflet stays inside. The batch number taken from the box is enough to contact the maker.

Can you mix two liquids of different strengths?

Yes, and the final strength can be worked out by dividing the total nicotine by the total volume. For example, 10ml at 12mg/ml mixed with 10ml at 0mg/ml gives 20ml at 6mg/ml. The bottle mixer on our home page does this sum for up to three bottles.

Read vape liquid from the bottle, then judge the flavour

The front sets compatibility with your kit, the back and cap show whether the bottle meets UK rules, the leaflet explains how to store it. Flavour comes last, once the bottle has answered the questions that matter.

The same method works for every bottle on this shelf, from a ready-to-vape 10ml to a shortfill waiting for its shots. Read in that order, vape liquid can be chosen in seconds, and surprises at the first refill become rare.

On the same shelf

Written for adult readers only. Vaping products usually contain nicotine, which is addictive, and nicotine vaping products are not for sale to under-18s in the UK. La Fiole Bleue describes bottles and labels, and nothing here is a buying recommendation.