CBD can cause unwanted effects, including tiredness, diarrhoea and changes in appetite, and it may interact with other medicines. The risks deserve extra care during pregnancy or breastfeeding and when use in children is being considered. Before starting CBD gummies, ask a prescriber or pharmacist to review your medicines, health circumstances and reasons for use.
The fair summary up front: the World Health Organization reviewed the evidence and concluded CBD is generally well tolerated with a good safety profile and no abuse or dependence potential WHO, 2018, and the TGA reached a similar view of low-dose CBD when it down-scheduled it TGA. That's a genuinely good starting point. The rest of this article is about the exceptions — because the exceptions are where safety actually lives.
The Common Side Effects: Mild, But Real
Across clinical trials, the side effects reported most often are dry mouth, drowsiness, diarrhoea, reduced appetite and fatigue Mayo Clinic. A few practical notes the labels skip:
- Drowsiness cuts both ways. It's a feature if you're taking gummies for sleep; it's a problem at 10 am before a meeting or a drive. Higher doses and full-spectrum products make it more likely.
- Digestive effects are often dose-dependent — and gummies add their own variables (sweeteners like sorbitol can cause GI upset entirely independent of CBD, a confusion worth knowing about before you blame the cannabinoid).
- Side effects tend to appear early and settle — but "settle" isn't guaranteed, and anything persistent is a conversation with your prescriber, not something to push through.
The Liver Signal: Worth Knowing, Not Panicking About
In a randomised, double-blind FDA trial of healthy adults taking CBD daily for 28 days, 5.6% experienced liver enzyme (ALT) elevations consistent with drug-induced liver injury signals — at a dose of 5 mg/kg, i.e. around 350 mg daily for a 70 kg person Florian et al., 2025, JAMA Internal Medicine. Earlier research found the risk concentrates at high doses — above roughly 1,500 mg/day — and rises sharply when CBD is combined with certain medications, particularly the anti-epileptic valproate Chen et al., 2024.
What this means in practice: at typical gummy doses the absolute risk looks low, but it's not zero, it's dose-related, and it's exactly why Australia's prescription pathway — with a doctor who can order a liver function test if warranted — is a feature rather than a nuisance. Anyone with existing liver disease should treat that conversation as mandatory, not optional.
Drug Interactions: The Section That Matters Most
If you take one thing from this article, make it this: CBD is processed by the same liver enzyme system — the cytochrome P450 family — that handles a long list of common medications, and it can inhibit those enzymes, raising or lowering the blood levels of drugs you're already taking Balachandran et al., 2021. One interaction database lists over 700 drugs with known CBD interactions Drugs.com.
The grapefruit rule of thumb. Many medication labels carry a warning about grapefruit juice — because grapefruit inhibits the same enzymes. CBD works through a similar mechanism, so a useful screening heuristic is: if your medication has a grapefruit warning, treat CBD as a live interaction question for your pharmacist Healthline Bailey et al., 2013. It's a rule of thumb, not a guarantee in either direction — some interacting drugs carry no grapefruit warning — which is why the pharmacist conversation is the real answer.
The medication classes with the best-documented concerns:
- Blood thinners. CBD inhibits CYP2C9, the enzyme that clears the active form of warfarin — a combination documented to increase anticoagulant effect and bleeding risk Healio. This is the highest-stakes interaction on the list.
- Antidepressants and psychiatric medications. CBD may increase blood levels of SSRIs, tricyclics and some antipsychotics — relevant precisely because anxiety and low mood are top reasons people try CBD Harvard Health.
- Anti-epileptics. Interactions here are so well documented (valproate's liver-enzyme effect, clobazam's level increases) that they're part of prescribing guidance for Epidyolex.
- Opioids and sedatives. Additive drowsiness is the concern — including with codeine-containing painkillers.
- Anything with a narrow therapeutic window, where small changes in blood level matter — thyroid medication, some immunosuppressants, certain heart drugs.
The good news: your pharmacist can check a specific combination in about two minutes, and in Australia a prescriber is already in the loop by design. Use both.
Who Should Avoid CBD Gummies Altogether
Some situations call not for caution but for abstinence, on current evidence:
- Pregnancy and breastfeeding. The FDA strongly advises avoiding CBD in any form during pregnancy and lactation — the safety data simply don't exist, and what we know about cannabinoid transfer to the baby is not reassuring FDA CDC. Australian guidance aligns. This is a "no," not a "ask first."
- Children and adolescents, outside specialist care. The only paediatric CBD use with evidence and approval is pharmaceutical-grade CBD for specific epilepsy syndromes under specialist supervision Child Mind Institute. There is no basis for giving children retail gummies — and gummies' lolly-like appearance makes secure storage a genuine household safety issue, full stop.
- People with significant liver disease — see the section above; specialist guidance only.
- Anyone about to drive or be drug tested, if the product contains any THC — details below.
- Pets. Covered in Beyond the Big Three, but worth repeating in a safety article: no cannabis product is registered for animals in Australia, and online "pet gummies" bypass every protection that exists AVA. Vet first, always.
Driving and Drug Testing: The Australian Practicalities
When it comes to Australian roadside drug testing, the substance tested for is THC, not CBD. That distinction matters for driving law specifically, but it does not make CBD a free pass: it can still cause side effects such as tiredness and can interact with other medicines. Products may also contain more THC than expected, so no product can promise a safe drive or a negative test. ADF RACGP/AJGP
The legal landscape is shifting — NSW passed legislation in September 2026 creating a medical defence for prescribed patients below a THC threshold, though it had not commenced at the time of writing, and other states still run zero-tolerance presence offences Transport for NSW. Practical guidance: if driving matters to you, choose isolate or broad-spectrum products with a lab report showing THC as not detected, and keep the COA. If you're prescribed a THC-containing product, treat "don't drive" as part of the prescription unless your state says otherwise.
Workplace testing follows the same logic. Standard panels target THC, not CBD — but trace THC in full-spectrum products, or mislabelled products, can trigger a positive Prisma Health. If your employment involves testing, that risk belongs in the prescriber conversation, and your workplace policy matters as much as the law.
Older Adults: A Note on the Fastest-Growing User Group
Older Australians are one of the quickest-growing CBD demographics, largely for pain and sleep Porter et al., 2021. They're also the group where the interaction section bites hardest — polypharmacy is the norm, not the exception — and where drowsiness carries fall risk. None of this rules CBD out; all of it argues for the prescription pathway doing its job: medication review first, low starting doses, and someone checking the whole picture US Pharmacist.
The Practical Safety Checklist
Before starting CBD gummies, you should be able to tick: your prescriber knows your full medication list (including supplements and the occasional things); a pharmacist has sanity-checked the big interaction risks; you're not pregnant, breastfeeding, or buying for a child or pet; you've chosen a product with a batch-matched lab report (see How to Choose Quality Gummies); you've thought through driving and workplace testing; and you know what side effect would make you stop and call the doctor. That list isn't bureaucratic fuss — it's the difference between CBD's genuinely decent safety record applying to you, or not.
The Bottom Line
Next reads: Dosage Guide: Starting Low, Going Slow · How to Choose Quality Gummies · Are CBD Gummies Legal in Australia?
This article is general information — not medical advice. Always discuss medications and supplements with your doctor or pharmacist.
Sources and last checked: 20 October 2026
- WHO (2018), Cannabidiol Critical Review Report — cdn.who.int
- Florian et al. (2025), CBD and liver enzyme elevations in healthy adults: RCT — JAMA Internal Medicine
- Chen et al. (2024), Metabolism and liver toxicity of CBD — PMC11404724
- Balachandran et al. (2021), CBD interactions with medications — PMC8298645
- Drugs.com — Cannabidiol interactions checker — drugs.com
- Healio (2022) — Cannabinoids and drug interactions with cardiovascular medications — healio.com
- Harvard Health — CBD and other medications: proceed with caution — health.harvard.edu
- Bailey et al. (2013), Grapefruit–medication interactions — PMC3589309
- FDA — Using CBD when pregnant or breastfeeding — fda.gov
- CDC — Cannabis and breastfeeding — cdc.gov
- Child Mind Institute — CBD: what parents need to know — childmind.org
- Mayo Clinic — CBD: safe and effective? — mayoclinic.org
- ADF — Roadside drug testing — adf.org.au
- RACGP/AJGP (2021) — Medical cannabis and driving — racgp.org.au
- Transport for NSW — Medical cannabis and driving reforms — transport.nsw.gov.au
- Prisma Health — Does CBD cause a positive workplace drug test? — blog.prismahealth.org
- Porter et al. (2021), CBD use by older adults — PMC8344100
- US Pharmacist — Cannabidiol use in older adults — uspharmacist.com
- Australian Veterinary Association — Medicinal cannabis in animals — ava.com.au
- TGA — Over-the-counter access to low dose cannabidiol — tga.gov.au