CBD and Levothyroxine (e.g. Eutirox, Levoxyl, L-Thyroxin, Thyrox, Thyronorm)

This guide is for people who take L‑thyroxine (levothyroxine; e.g. Eutirox, Levoxyl, L‑Thyroxin, Thyrox, Thyronorm) and are considering using CBD oil alongside it – for example in connection with pain, sleep or stress. This article explains what is known about CBD and levothyroxine interactions, how to separate the timing of both substances, which warning signs to look out for, and how to monitor your thyroid levels. More on how CBD is discussed in relation to the body can be found here: CBD and the endocannabinoid system.

Can I use CBD and L‑thyroxine (levothyroxine) together?

What we know about CBD and levothyroxine

Robust clinical studies specifically on “CBD and levothyroxine” are not currently available. From a theoretical perspective, CBD may inhibit certain liver enzymes and in this way influence drug levels. For levothyroxine it is relevant that it is mainly eliminated through deiodination and hepatic conjugation (including UGT); CYP enzymes play a lesser role. Plausible interaction points concern absorption (when taken at the same time), protein binding and UGT enzymes. In practice, this means that careful monitoring tends to be more useful than blanket restrictions.

What we do not know

It is not sufficiently studied whether, and from which CBD dose onwards, TSH or fT4 may change in a clinically relevant way in people who are stable on L‑thyroxine. There are individual reports, but systematic data are lacking. A cautious approach is therefore advisable: start carefully, keep an interval between products, and check your levels.

Timing of intake: how to combine L‑thyroxine and CBD

How to take L‑thyroxine (levothyroxine)

• Take in the morning 30–60 minutes before breakfast – with water only.
• Alternative: take in the evening 3–4 hours after the last meal.
• Keep a gap of 4 hours before or after calcium, iron, soya, antacids and high‑fibre supplements.

How to schedule CBD alongside levothyroxine

• Do not take CBD at the same time as L‑thyroxine; leave at least a 4‑hour interval.
• Practical plan: L‑thyroxine in the morning on an empty stomach, CBD in the evening.
• Titrate slowly (for example, start with 5–10 mg in the evening) and observe how you feel and any side effects: CBD dosage.

CBD–levothyroxine interaction: what is plausible?

• Absorption: Taking both substances at the same time may interfere with absorption. This is why a 4‑hour interval is usually recommended.
• Liver metabolism: Levothyroxine is mainly deiodinated and conjugated (UGT). CBD may inhibit UGT as well as CYP3A4 and CYP2C19, but its direct impact on L‑thyroxine is regarded as limited.
• “Grapefruit effect”: CBD may, in some respects, affect certain enzymes in a similar way to grapefruit. More on this: CBD interactions.
• Protein binding: Theoretical shifts are possible; the clinical relevance is unclear – therefore it is sensible to pay attention to symptoms and laboratory values.

Overview of possible side effects

CBD (systemic use)

• Commonly reported: tiredness/drowsiness, dry mouth, loose stools/nausea, changes in appetite/weight.
• Less common: increases in liver enzymes, particularly at higher doses or in people who are more sensitive.
• Pay attention to quality: reliable information on mg content, certificate of analysis (CoA), residual THC content, tests for pesticides/heavy metals.

Levothyroxine (L‑thyroxine)

• Narrow therapeutic range; symptoms often indicate over‑ or under‑replacement.
• Possible signs of over‑replacement: rapid heartbeat, tremor, nervousness, sleep disturbances, weight loss, heat intolerance.
• Possible signs of under‑replacement: tiredness, weight gain, sensitivity to cold, constipation, dry skin.
• After a dose change: levels are typically checked after 6–8 weeks.

Monitoring: TSH/fT4 and symptom check when using CBD

• Baseline: document TSH and fT4 before starting CBD.
• Control: recheck after 6–8 weeks (half‑life of T4 is around 7 days); if you notice marked symptoms, contact a healthcare professional earlier.
• Observe symptoms: palpitations, inner restlessness, sleep problems, increased sweating (more suggestive of overactivity) vs. pronounced tiredness, feeling cold, weight gain (more suggestive of underactivity).

Example: A person with Hashimoto’s thyroiditis, stable on 100 µg L‑thyroxine, starts 10 mg CBD in the evening, 4 hours after dinner. Suggested approach: TSH/fT4 before starting, repeat after 6–8 weeks; in the event of palpitations or pronounced tiredness, seek medical advice sooner.

Who should be particularly cautious with CBD and levothyroxine?

• Pregnant and breastfeeding people.
• Older adults or people with cardiac arrhythmias or coronary heart disease.
• Those taking multiple medicines, especially with a narrow therapeutic window or with significant liver metabolism.
• People with liver disease or raised liver enzymes.

Use in everyday life: schedule and safety checklist

Simple daily schedule for CBD and L‑thyroxine

• Morning: L‑thyroxine on an empty stomach with water (30–60 minutes before breakfast).
• During the day: keep a 4‑hour gap before or after calcium/iron/antacids and similar supplements.
• Evening: take CBD, ideally 4 hours after L‑thyroxine and after the last main meal.

Checklist before starting CBD with levothyroxine

• Note your levels: current TSH and fT4.
• Start low and increase slowly: CBD dosage.
• Check product quality: CoA, clear mg information, THC content, contaminant testing.
• Form of administration: systemic forms (oils/capsules) are more relevant for potential interactions; topical products are generally considered to carry a lower interaction risk.
• Inform yourself: overview of CBD drug interactions, liver enzymes (CYP3A4, CYP2C19, UGT) and the “grapefruit effect”: CBD interactions.

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.