Medical cannabis means cannabis or cannabinoid products used to treat a diagnosed condition under the supervision of a qualified prescriber, made to a defined and consistent quality and supplied on prescription. That separates it from recreational use in three ways: there is a diagnosis, there is a prescriber who is accountable for the decision, and the product has a known composition. The strength of the scientific evidence varies a great deal from one condition to another, and that is the part most often overstated. This page explains the term and the evidence; it does not give treatment or dosing advice, and it does not repeat our separate posts on routes of administration, dosing and contraindications.
Two different things share one label
“Medical cannabis” is used for two quite different groups of products.
Approved cannabinoid medicines. These have been through a full marketing authorisation, with clinical trial data reviewed by a regulator. The US Food and Drug Administration states that it has not approved a marketing application for cannabis itself for any disease or condition, but it has approved one cannabis-derived and three cannabis-related drug products, all available only on prescription:
| Medicine | Active substance | Use stated by the regulator or guideline cited |
|---|---|---|
| Epidiolex (Epidyolex in the EU) | Purified cannabidiol (CBD) | Seizures in Lennox-Gastaut syndrome, Dravet syndrome and tuberous sclerosis complex |
| Marinol, Syndros | Dronabinol, a synthetic THC | Uses including anorexia with weight loss in AIDS patients |
| Cesamet | Nabilone, a synthetic compound similar to THC | Considered in UK guidance as an add-on for persistent chemotherapy-induced nausea and vomiting |
| Nabiximols (Sativex) | THC and CBD oromucosal spray | Add-on therapy for moderate to severe spasticity in multiple sclerosis |
Prescribed cannabis products. Dried flower, oils and extracts prescribed by a doctor or other authorised practitioner without a product-specific marketing authorisation. Thailand’s system is of this kind. Such products can be made to pharmaceutical quality standards, but the evidence behind them is the general body of cannabis research, not a trial package for that exact product.
What pharmaceutical quality adds
For a medicine, quality means the product in the pack is what the label says, batch after batch. The European Medicines Agency summarises the aim of good manufacturing practice as making sure medicines are of consistent high quality, appropriate for their intended use and in line with their authorisation. Our separate post on GMP for medical cannabis covers what this means inside a facility. The point here is simpler: a prescriber cannot make a reasoned decision about a product whose cannabinoid content changes from one batch to the next.
How strong is the evidence?
The most cited independent review is the 2017 report of the US National Academies of Sciences, Engineering, and Medicine (NASEM), which graded the evidence condition by condition. Its therapeutic conclusions, in short:
| Level of evidence (NASEM 2017) | Conditions |
|---|---|
| Conclusive or substantial | Chronic pain in adults (cannabis); chemotherapy-induced nausea and vomiting (oral cannabinoids); patient-reported multiple sclerosis spasticity (oral cannabinoids) |
| Moderate | Short-term sleep outcomes in people with sleep disturbance linked to sleep apnoea, fibromyalgia, chronic pain or multiple sclerosis (mainly nabiximols) |
| Limited | Appetite and weight loss in HIV/AIDS; clinician-measured MS spasticity; Tourette syndrome; anxiety in a public-speaking test (CBD); PTSD (one small trial of nabilone) |
| No or insufficient | Cancers including glioma; cancer-associated anorexia; irritable bowel syndrome; epilepsy; symptoms of Parkinson’s disease; dystonia; achieving abstinence from addictive substances |
NASEM defines “limited” as weak evidence with significant uncertainty, and “no or insufficient” as mixed findings, a single poor study or no study at all. Three cautions follow from that.
- The grades apply to specific product types. “Oral cannabinoids” for nausea means pharmaceutical THC-type medicines, not any cannabis product.
- Insufficient is not the same as ineffective. It means the studies available were too few or too weak to decide. Epilepsy shows why this matters: the 2017 review rated the evidence insufficient, yet purified CBD is now approved in the US and the EU for seizures in specific rare epilepsy syndromes.
- Guideline bodies can weigh the same studies differently. The UK guideline from NICE on cannabis-based medicinal products says to consider nabilone as an add-on for adults whose chemotherapy-induced nausea persists despite optimised standard antiemetics, and to offer a 4-week trial of THC:CBD spray for moderate to severe MS spasticity when other treatments have not worked. For chronic pain in adults, however, it says not to offer nabilone, dronabinol, THC or THC with CBD, and not to offer CBD except within a clinical trial. The condition NASEM rated “substantial” is one where NICE advises against routine use.
The Thai “medical cannabis certificate” is a prescription
Searches for a “medical cannabis certificate” in Thailand usually mean the prescription that lets a member of the public buy cannabis flower. Under the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568, public retail sales of flower are allowed only against such a prescription. The official form, PT 33, titled “Prescription for Controlled Herb (Cannabis)”, shows how the system works:
- Who can issue it: a licensed medical doctor, Thai traditional or applied Thai traditional medicine practitioner, dentist, pharmacist, traditional Chinese medicine practitioner or folk healer.
- What it records: the patient’s identity, the diagnosed condition, the prescribed quantity and the number of days.
- Time limit: a prescription may not exceed 30 days per issuance.
- Clinical basis: the diagnosis must match the treatment guidelines and indications approved for the prescriber’s profession, and be consistent with other medical documents supporting the patient’s use.
- Record keeping: the business that dispenses must keep the prescription for one year.
A PT 33 is not a licence to possess cannabis anywhere else, and it does not turn cannabis flower into an approved medicine in the regulatory sense described above. On 22 September 2026 the Cabinet approved the draft Cannabis Control Act (formerly the Cannabis and Hemp Act), whose primary purpose is to limit cannabis use strictly to medical purposes on a doctor’s prescription. It has gone to the House of Representatives and is not yet in force.
Common mistakes
- Treating a CBD product on a shop shelf as medical cannabis. Without a diagnosis, a prescription and a defined product, it is not.
- Reading “substantial evidence for chronic pain” as proof for every pain condition. The finding concerns adults with chronic pain as a group, and NICE still advises against routine use.
- Reading “insufficient” as “proven not to work”. It means the question is still open.
- Using the approved-medicine list to justify flower. Approval of a purified substance for named syndromes says nothing about cannabis flower in general.
- Carrying a Thai prescription abroad. Cannabis remains a serious illegal drug in several countries, and Thai authorities tell travellers to check the law at their destination.
Discuss any treatment decision with a qualified prescriber, and check the current Thai rules, which have changed repeatedly since 2022.