What Else Is in the Tablet? A 2026 Guide to Excipients in UK Medicines

When patients open a medicine box, attention usually falls on the active ingredient: the paracetamol, the antibiotic, the blood-pressure tablet. Yet every medicine is more than its active substance. Tablets, capsules, liquids and creams also contain excipients — ingredients that have no intended therapeutic effect but are essential to how a medicine is made, stored, released and tolerated.

The word “inactive” can be misleading. Excipients are not intended to treat the condition, but they are not always biologically inert. For most people they cause no difficulty. For a smaller group, however, an excipient may be the reason a medicine is unsuitable, unacceptable or worth discussing before the first dose.

What excipients actually do

Excipients perform practical roles. Fillers give a tablet its size; binders hold it together; disintegrants help it break down in the stomach; lubricants prevent sticking during manufacture; coatings protect the active ingredient or mask a taste. Liquid medicines may contain preservatives, sweeteners, flavourings and solvents. Capsules may use gelatin. Some products contain lactose, ethanol, aspartame, propylene glycol, arachis oil, sesame oil, soya or gluten-derived ingredients.

The important distinction is between an excipient’s function and its risk. An ingredient listed on a patient information leaflet (PIL) is not, by itself, evidence of danger. The relevant questions are usually: how much is present, how the medicine is taken, and whether the individual patient has a specific sensitivity, dietary requirement or clinical vulnerability.

Why the same medicine comes in different formulations

Two products containing the same active ingredient may contain different excipients. This is common among generic medicines, where manufacturers may use different fillers, coatings, sweeteners or preservatives while meeting the same standards of quality, safety and efficacy. A change of supplier can therefore mean a change of excipients even when the medicine name and dose look familiar.

For most patients this has no practical consequence. For someone who has reacted to a specific ingredient, or who follows a restricted diet, it can matter a great deal. It is sensible to record the exact product name, strength and batch where possible, rather than assuming that all versions of a medicine will behave identically.

Reading the patient information leaflet without alarm

The PIL is the most accessible starting point. Section 2 usually sets out what a patient needs to know before taking the medicine, including warnings about particular excipients. Phrases such as “contains lactose” or “contains aspartame” are factual statements. They do not mean that the product is unsafe for everyone.

For example, a leaflet may state that a tablet contains a small amount of lactose. This is generally relevant to people with severe lactose intolerance, not to everyone who avoids dairy for preference. Cow’s milk allergy is a different matter from lactose intolerance, and the two should not be treated as interchangeable. Similarly, aspartame is relevant to people with phenylketonuria because it is a source of phenylalanine; for the wider population, the warning does not imply a general hazard.

Healthcare professionals can consult the Summary of Product Characteristics (SmPC), which gives more detailed information about qualitative and quantitative excipient content. Patients who need that level of detail can ask a pharmacist to check the relevant product information.

When an excipient deserves a conversation

An excipient is worth flagging when there is a clear personal reason: a previous allergic reaction to a medicine or ingredient, a known sensitivity, a strict dietary or religious requirement, or a clinical condition that makes a particular excipient less suitable. Examples might include a documented reaction to arachis oil or soya, a need to avoid alcohol-containing liquids, or a question about gelatin in a capsule.

True allergy to an excipient is uncommon, but it should not be dismissed. If a patient has had swelling, breathing difficulty, widespread rash or another significant reaction after a medicine, they should seek urgent advice as appropriate and tell their pharmacist or prescriber. Suspected adverse reactions can also be reported through the UK Yellow Card scheme.

Equally, not every unpleasant effect is an allergy. Headache, nausea or loose stools after a medicine may relate to the active ingredient, the illness itself or another cause. A pharmacist can help separate a plausible excipient issue from a coincidence or a more general side-effect pattern.

Dietary and religious considerations

Some patients ask about gelatin because it may be derived from bovine or porcine sources. Others ask about ethanol in oral liquids, lactose in tablets or the suitability of a product for a vegan diet. These are legitimate questions, and the answer is product-specific rather than universal.

A pharmacist may need to check the manufacturer’s information to confirm the source of an ingredient. In some cases an alternative formulation exists; in others it may not, or switching could affect how the medicine is absorbed or monitored. Religious and ethical judgments are personal, and clinical need may need to be weighed alongside them. The practical step is to ask before deciding, rather than to assume that a capsule is necessarily pork-derived or that a “sugar-free” liquid is automatically suitable for every dietary pattern.

Asking for an alternative

Patients who are concerned about an excipient should say so clearly at the pharmacy counter or in a prescribing consultation. It helps to name the ingredient, describe the previous reaction or requirement, and ask whether another formulation of the same active ingredient is available. In community pharmacy, a pharmacist can check product information and advise on options. For prescribed medicines, a change may require a new prescription or a conversation with the prescriber.

It is important not to stop a prescribed medicine abruptly without advice. Some alternatives involve different doses, different release profiles or additional monitoring. A switched product may also contain a different set of excipients, so the check needs to be repeated rather than assumed.

A balanced view

Excipients are assessed as part of the UK marketing authorisation process, and their presence does not mean a medicine is contaminated or unsafe. They are there for reasons of manufacture, stability and patient acceptability. The sensible approach is neither to ignore the ingredient list nor to treat every additive as a threat.

Reading the PIL, keeping a note of any confirmed medicine allergy, and asking a pharmacist about specific concerns are simple steps. For most patients, the fine print will remain just that. For those with a genuine need, however, understanding excipients can turn an unexplained worry into a practical conversation about the right medicine.