How It's Taken
The form changes almost everything: how fast it works, how long it lasts, and how easy it is to get the dose right.
There's no single way to take medical cannabis. A prescribed product might be an oil you drop under your tongue, a spray, a capsule, or dried flower you inhale through a vaporiser. Each behaves differently in how fast it works, how long it lasts, and how precisely you can control the dose. Which one a specialist chooses depends on the condition, the person, and how quickly an effect is needed.
The main forms
Oils and tinctures are the most common unlicensed prescription. You measure drops under the tongue, and the effect comes on gradually over roughly 30–90 minutes and lasts several hours. Because it's slow and steady, it's easier to build up carefully, but harder to fine-tune in the moment.
Capsules (including the licensed medicines Nabilone and the CBD solution Epidyolex) give a fixed, consistent dose, swallowed and absorbed through the gut like any other tablet. Slow onset, long-lasting, and very predictable dose to dose.
Oromucosal spray (the licensed MS medicine Sativex) is sprayed inside the mouth, absorbed through the lining, and sits between an oil and inhalation for speed. Doses are counted in sprays and titrated up slowly.
Dried flower, vaporised. Some unlicensed prescriptions are for cannabis flower used in a medical vaporiser that heats it without burning. Inhaled, the effect arrives within minutes and fades within a few hours, which makes it useful for symptoms that flare quickly. But the fast, strong onset also makes it the easiest form to overshoot with. Prescribed flower is meant to be vaporised, not smoked: smoking adds the harms of combustion and tar, which is the whole reason safer routes matter.
Why dose and "titration" matter so much
The word you'll hear from any good clinic is titration: starting low and increasing slowly until you find the smallest dose that helps. It sounds cautious because it is, and for good reason: get it wrong and you either feel nothing or feel too much. STRONGEvidence strength "Start low, go slow" is the standard, well-established principle for cannabis dosing, especially with any THC-containing product, and above all for anything eaten or swallowed, where the effect is delayed and easy to stack by mistake. Why: people vary enormously in how they respond, and a delayed-onset form tempts you to take more before the first dose has landed. The same logic behind edibles catching people out applies to medical oils and capsules.
This is also where the medical setting earns its keep: a labelled product with a known THC and CBD content lets you titrate meaningfully, because "one more drop" is an actual, repeatable amount, not a guess, as it always is with illegal-market cannabis.
Side effects and cautions
Medical cannabis is generally reasonably well tolerated, but it is not side-effect-free, particularly the THC-containing products. Common effects include dizziness, drowsiness, dry mouth, nausea and changes in appetite. Higher-THC products can cause the same intoxication, anxiety or "off" feeling as recreational cannabis. MIXEDEvidence strength Reported side effects of cannabis-based medicines commonly include dizziness, sedation, dry mouth and nausea; THC-rich products carry the added risk of intoxication and, in some people, worse anxiety. Evidence on longer-term harms and on dependence from medical use is still limited. Sources: NHS · Medical cannabis; adverse-effect findings summarised in the 2025 AHRQ living review.
Three practical cautions worth flagging. Dependence: regular THC use can lead to tolerance and dependence. The medical label doesn't switch that off, so it's covered honestly in Tolerance & Dependency. Interactions: cannabinoids can interact with other medicines, which is exactly why a prescribing specialist reviews your full list rather than you adding it yourself. Driving and work: a THC product can leave you unfit to drive and will show on a workplace drug test the same as any other cannabis. The legal side of that is on The Law Around the World.
None of this is a how-to for self-dosing. If a cannabis-based medicine is on the table for you, the dose, the form and the plan are things to work out with a specialist. This page is here so you understand the choices, not so you make them alone.