CBD and Metformin (e.g. Glucophage, Metformin-Ratiopharm, Metformax)

CBD and Metformin (e.g. Glucophage, Metformin‑Ratiopharm, Metformax) are sometimes taken together by people with type 2 diabetes who are interested in CBD for wellbeing or symptom support. Metformin is barely metabolised by liver enzymes and is largely excreted unchanged via the kidneys, whereas CBD can influence liver enzymes and, in laboratory studies, certain transport proteins. For Metformin, any possible CBD interaction is therefore considered more likely at the level of transporters (such as OCT/MATE) rather than hepatic metabolism. Current evidence on a “CBD Metformin interaction” is limited, so a cautious, medically supervised approach is recommended.

• Metformin is mostly excreted unchanged via the kidneys; transport proteins (OCT1/2, MATE1/2‑K) regulate uptake and elimination.
• CBD can inhibit enzymes (CYP450) and, in laboratory studies, also transporters (e.g. P‑gp, BCRP; possibly MATE/OCT).
• Any CBD–Metformin interaction risk is therefore more theoretical and likely related to transporters rather than liver metabolism.
• If you use both, start low with CBD, keep a time gap, take with/after food, and monitor blood glucose closely for 2–4 weeks.
• Watch for warning signs (e.g. deep/rapid breathing, pronounced tiredness, persistent gastrointestinal symptoms) and speak to your doctor – especially if you have reduced kidney function.

What is CBD? Mechanisms of action without intoxicating effects

CBD is one of over 100 identified cannabinoids found in the cannabis plant. Unlike THC, CBD does not have an intoxicating effect and is therefore often discussed in wellness and medically related contexts. Instead of binding “directly” to CB1/CB2 receptors, CBD is thought to modulate the endocannabinoid system more indirectly and to influence other targets, such as 5‑HT1A, TRPV1 and adenosine receptors. CBD can also inhibit enzyme systems (including CYP450) and transporters (e.g. P‑gp/ABCB1, BCRP/ABCG2), which may be relevant for potential CBD drug interactions with prescription medicines. The extent of these effects depends on dose, product quality and individual factors. Read our article on how CBD acts in the body.

Endocannabinoid system and other targets

• Endocannabinoid system: indirect modulation of CB1/CB2 receptors.
• Other targets: 5‑HT1A, TRPV1 and adenosine receptors.
• Enzymes/transporters: inhibition of CYP450 (especially CYP2C19, CYP3A4, among others) and in vitro indications of transporter inhibition (e.g. P‑gp, BCRP).
• No psychoactive or intoxicating effect comparable to THC.

CBD interactions with medicines

Metformin: Action, elimination and transporters

Metformin is a standard medicine for type 2 diabetes (e.g. Glucophage, Metformin‑ratiopharm). It is commonly used to help lower blood glucose by reducing hepatic glucose production and improving insulin action in peripheral tissues. From a pharmacokinetic perspective, Metformin is barely metabolised by liver enzymes. Instead, it is predominantly excreted unchanged via the kidneys.

Transport proteins play a key role in cellular uptake and excretion – in particular OCT1/2 (uptake) and MATE1/2‑K (renal tubular secretion). In people with impaired kidney function, Metformin can accumulate in the body; eGFR should be checked regularly.

OCT1/2, MATE1/2‑K – why these proteins matter

• OCT1 (liver) and OCT2 (kidney) support uptake of Metformin into cells.
• MATE1/2‑K (kidney) transport Metformin into urine and influence its clearance.
• Consequence: inhibition of these transporters could theoretically increase Metformin levels in the body.

Because CBD may affect some transport proteins in laboratory studies, these mechanisms are relevant when considering a potential CBD and Metformin interaction.

CBD and Metformin: Potential interaction mechanisms

Important: Metformin is largely excreted unchanged via the kidneys and depends on OCT and MATE transporters for uptake and elimination. CBD can influence both CYP enzymes and certain transporters in vitro. For CBD and Metformin, any interaction risk is therefore mainly a theoretical consideration at transporter level rather than through liver metabolism.

Transporter inhibition (in vitro) vs clinical data

• CBD primarily inhibits CYP enzymes; in vitro there are indications of inhibition of transporters such as P‑gp (ABCB1) and BCRP (ABCG2). For MATE/OCT, the evidence largely consists of preclinical or indirect data.
• Because Metformin is transported via OCT/MATE, a theoretical CBD Metformin interaction via transporters is conceivable (reduced renal secretion → higher Metformin exposure).
• Robust clinical studies specifically examining CBD and Metformin used together are largely lacking. Therefore, an individual and cautious approach is advisable.
• Overlapping side effects (nausea, diarrhoea, tiredness) may make it more difficult to recognise low or high blood glucose levels.

Practical precautions for combining CBD and Metformin

• Start low, go slow: begin with 5–10 mg CBD/day, increasing slowly every 3–7 days – only in consultation with your doctor.
• Timing: as a precaution, keep a 2–3 hour interval between taking CBD and Metformin (evidence is limited; this is a precautionary measure).
• With food: take CBD with/after a meal – important, as Metformin can also irritate the gastrointestinal tract.
• Monitoring: check blood glucose more frequently in the first 2–4 weeks after starting CBD or changing the CBD dose (e.g. daily, including fasting and post‑meal readings).
• Kidney function: Metformin is contraindicated at eGFR < 30 ml/min; if kidney function is reduced, seek medical advice before starting CBD.
• If you experience persistent diarrhoea, pronounced nausea or unusual tiredness, contact your doctor.

Note: Use our interaction checker as an additional tool – it does not replace medical advice.

Side effects compared: CBD vs Metformin

Overlap and what it means for you

Overlapping side effects of CBD and Metformin are mainly gastrointestinal symptoms (nausea, diarrhoea) and tiredness/dizziness. These can make it harder to notice low or high blood glucose. Pay attention to how you feel and adjust your monitoring schedule accordingly.

CBD and Metformin: Dose, timing, monitoring

If, after medical advice, you decide to use CBD while taking Metformin, a structured plan can help you and your doctor to monitor safety.

1. Discuss with your doctor: review all medicines, eGFR/kidney function, liver function, target glucose values and a monitoring plan.
2. Starting dose: 5–10 mg CBD/day for 3–7 days; increase in small steps only if needed and tolerated.
3. Timing: take CBD with/after a meal, keeping a 2–3 hour interval from Metformin as a precaution.
4. Monitoring plan: for 2–4 weeks after starting or changing CBD, monitor blood glucose more closely (fasting and after meals) and record any symptoms.
5. Follow‑up: arrange a follow‑up appointment after 2–4 weeks to review blood glucose, side effects and any need for adjustments.

Practice box: Safety check before starting CBD

• Is eGFR/kidney function up to date?
• Are you taking other diabetes medicines or multiple prescription medicines (polypharmacy)?
• Which CBD starting dose and form (oil/capsules) are planned?
• Is a blood glucose monitoring plan for the next 2–4 weeks agreed?
• Has a follow‑up appointment with your doctor been arranged?

Checklist for your medical consultation

• Current Metformin dose and timing.
• Recent kidney function (eGFR), liver function tests, vitamin B12 levels if available.
• Planned CBD dose and product; information on product quality (certificate of analysis/CoA).
• Monitoring plan (frequency, target ranges) and clear warning signs that should trigger medical contact.
• Specific follow‑up date to review CBD and Metformin together.

Warning signs that need medical assessment

• Deep/rapid breathing, unusual tiredness, severe muscle pain.
• Persistent abdominal pain, nausea, vomiting or diarrhoea.
• Feeling cold, dizziness, light‑headedness.
• Signs of low or high blood glucose that you cannot manage as usual.
• Signs of an allergic reaction.

Who should be particularly cautious with CBD and Metformin?

• Older adults.
• People with reduced kidney or liver function.
• People taking multiple medicines (polypharmacy), especially additional diabetes medicines.
• Pregnancy/breastfeeding: CBD is generally not recommended.
• People at risk of vitamin B12 deficiency while taking Metformin (consider monitoring).

What does the research say about CBD and Metformin?

There are currently only limited clinical data on the specific combination “CBD and Metformin together”. However, there are in vitro findings on inhibition of transporters (e.g. P‑gp, BCRP; possibly MATE/OCT) by CBD, as well as more established evidence of CBD–CYP450 interactions (e.g. CYP3A4, CYP2C19). How far these laboratory findings apply to humans depends on dose, formulation and individual sensitivity. Overall, further research is needed before firm conclusions can be drawn about CBD Metformin interactions in routine clinical practice.

What is CBD and how does it act in the body? (Brief refresher)

CBD is one of more than 100 identified cannabinoids found in the cannabis plant. Unlike THC, it does not have a psychoactive effect and is often discussed in a medical context. CBD acts in the body by modulating the endocannabinoid system and influencing other targets such as 5‑HT1A, TRPV1 and adenosine receptors.

Read our article on how CBD acts in the body.

Metformin: Action – in brief

Metformin is a widely used medicine for type 2 diabetes. It is used to help reduce hepatic glucose production and increase insulin sensitivity. It is mainly excreted unchanged via the kidneys – therefore transport proteins (OCT/MATE) and kidney function are particularly relevant, especially when considering potential interactions with substances such as CBD.

Side effects of CBD

CBD is generally considered to have a favourable tolerability profile. Possible side effects include tiredness, dry mouth, dizziness, changes in appetite and gastrointestinal symptoms such as nausea or diarrhoea. These are usually mild and temporary. Start with a low dose, observe how you react and seek medical advice if side effects are persistent or severe. Pay attention to the quality of your CBD product (certificates of analysis/CoA).

Side effects of Metformin

Common: gastrointestinal symptoms (nausea, diarrhoea, abdominal pain), especially at the start. Less common: vitamin B12 deficiency; very rare: lactic acidosis. Regular medical check‑ups are advisable; Metformin is contraindicated at eGFR < 30 ml/min.

Disclaimer: This article is for information purposes only and does not replace medical advice. Do not change medicines or dosages without consulting your doctor. No claims are made regarding the treatment or cure of illnesses.