What is the Hepatic System and How Does it Work?

The liver helps determine what happens to cannabis after it enters your body. It changes THC and CBD into metabolites, influences how long they circulate, and can be affected by cannabinoids and their interactions with medicines. Understanding this process explains why an edible can feel very different from an inhaled product containing the same labeled amount of THC.

What Does the Hepatic System Include?

Hepatic means relating to the liver. The hepatic portal system is specifically the network of blood vessels that brings blood from digestive organs and the spleen to the liver. It is part of liver circulation, not another name for all liver functions. The hepatic artery supplies oxygen-rich blood, and hepatic veins carry blood away toward the heart.

The liver also produces bile, which travels through bile ducts into the intestine, with some stored in the gallbladder. As NIDDK explains, bile helps with fat digestion, while the liver stores and processes absorbed nutrients. Most dietary protein is broken into smaller components in the digestive tract before absorption; the liver subsequently uses and processes amino acids.

Other liver functions include maintaining blood glucose, making important blood proteins, processing bilirubin and converting many drugs into substances the body can eliminate. Metabolism does not always mean making a compound harmless. Some metabolites remain active, and some substances can injure liver cells during processing.

How the Liver Processes THC and CBD

After absorption, cannabinoids undergo chemical changes involving enzymes, including members of the cytochrome P450 family. THC can become 11-hydroxy-THC, an active metabolite, and then undergo further metabolism. CBD follows different metabolic pathways and does not produce the characteristic THC high, although it can cause drowsiness and other adverse effects.

These changes inside the body are different from cannabinoid degradation during storage. A product changing in a warm cupboard and a person metabolizing a dose are separate processes.

First-Pass Metabolism and Edibles

When a cannabinoid is swallowed, absorption through the gastrointestinal tract exposes it to intestinal and liver metabolism before much of it reaches the general circulation. This is called first-pass metabolism. It reduces the amount of unchanged drug reaching circulation but can also generate active metabolites.

With oral THC, formation of 11-hydroxy-THC contributes to the experience. It does not provide a universal conversion factor between an edible dose and an inhaled dose. Absorption, food, formulation and individual metabolism all matter. A slow onset is not evidence that an edible has failed.

Health Canada’s guidance on administration routes distinguishes rapid inhaled effects from the slower onset and later peak of swallowed products. Taking additional THC before the initial dose has fully developed can lead to unexpectedly strong and prolonged impairment.

Does Another Route Bypass the Liver?

• Smoking or vaping: cannabinoids absorbed through the lungs enter circulation without an initial passage through the liver. They still reach the liver later. Avoiding first-pass metabolism does not eliminate liver interactions or the respiratory risks of inhalation.
• Sublingual or buccal products: the portion absorbed through the mouth can avoid initial gastrointestinal first-pass metabolism. A swallowed portion follows the oral route. An oil held under the tongue is not guaranteed to be completely absorbed there.
• Topical products: ordinary creams are intended primarily for local application and should not be assumed to deliver a predictable systemic dose.
• Transdermal products: formulations designed to cross the skin may provide systemic delivery. This depends on the actual formulation and supporting evidence; it is not a property of every cannabis lotion or patch.

No route guarantees higher, more consistent bioavailability for every product. Choosing a medical formulation requires considering its evidence, dose, desired duration and risks, rather than treating liver bypass as an automatic advantage.

CBD and Liver Safety

A 2025 FDA randomized study tested oral CBD at 5 mg/kg per day for 28 days in healthy adults. The estimated proportion with liver enzyme elevations above three times the upper limit of normal was 5.6% in the CBD group, versus none in the placebo group. Participants did not experience liver-related symptoms, and enzymes returned to normal after discontinuation.

This does not mean every CBD user has a 5.6% risk: the finding applies to the studied dose, formulation, population and duration. It does demonstrate that absence of symptoms does not reliably establish liver safety, even in people without known liver disease.

The prescribing information for Epidiolex, a standardized CBD medicine for specified seizure disorders, requires liver testing and describes dose adjustments for moderate or severe hepatic impairment. It also addresses interactions, including increased concern with valproate. These prescribing instructions are not a dosing protocol for retail CBD.

Why Responses Differ Between People

Genetics, liver disease, other medicines, food and the product itself can change cannabinoid exposure. Older adults may also have greater sensitivity or take more interacting medicines; age alone does not tell you an individual’s metabolic rate.

Tell your clinician or pharmacist which THC and CBD products you use, their labeled amounts and how often you take them. Include supplements and nonprescription medicines. Do not assume changing from an edible to a vape removes an interaction, or stop prescribed treatment to accommodate a cannabis product.

Seek medical advice promptly for yellowing of the eyes or skin, dark urine, persistent vomiting or unexplained upper abdominal pain. If you have liver disease or use cannabinoids regularly alongside other medicines, an individualized review is more useful than trying to predict your response from someone else’s experience.