Your Liver Matters: Why a Safe Medication Dose May Depend on Your Liver Health
Key takeaways:
Your liver is the most important organ in your body for drug metabolism. Among other tasks, it processes and breaks down many medications you may be taking.
Your healthcare provider can perform blood tests to check how well your liver is functioning. These are called liver function tests (LFTs). Your provider might collect your LFTs during your regular wellness appointments.
If you have liver problems, your body may react to some medications differently. Depending on the medication, you may be told to take a lower dose or take it less often.
If you take a prescription medication, you may wonder how your healthcare provider settles on the best dosage for you. Your safety is the most important factor, but other reasons may also cross their mind. Among them, they may consider your body weight and medical history — which also includes your liver health.
There’s a similar trend for over-the-counter (OTC) medications. Recommended, labeled doses are provided by drug manufacturers with safety and appropriateness as top priorities.
You and your provider can work together to check how well your liver is working by performing routine blood tests. By keeping close tabs on how healthy and efficient your liver is, they can recommend a medication and dosage that’s safe for you.
Search and compare options
What role does the liver play in drug metabolism?
Your liver is the main organ involved in drug metabolism. After you eat your favorite snack, drink a beverage, or take your morning pills, your gut can start to break them down. After that, your gut can pass nutrients and medication into your bloodstream. From there, they can travel through your blood to your liver for additional processing.
Think of your liver as a filter. It breaks down and uses the substances you consume to clear them from your blood. It does this by making and deploying different enzymes (proteins). These enzymes can break down medications so they work as expected. This is why processing medications is one of your liver’s most important jobs.
In other words, your liver metabolizes many drugs. This is what makes them stop working over time. If your liver didn’t do this, medications could linger in your body for longer than desired and cause additional side effects.
Other medications, called prodrugs, only work after they’re activated by your liver. Prednisone is one common prodrug. This corticosteroid medication starts fighting inflammation after it's been processed by your liver.
How do liver problems affect drug metabolism?
Liver problems are caused by liver damage, which can happen for many reasons. Excessive alcohol intake, viral hepatitis, and obesity are all possible causes of liver damage. There are also varying degrees of liver damage, ranging from mild to severe.
In some cases, liver damage can stem from taking medications inappropriately or at an excessive dose. It can even happen when you take your medications exactly as prescribed. You and your healthcare provider can work together to prevent most causes of liver damage.
Read more like this
Explore these related articles, suggested for readers like you.
If you have liver problems, it’s harder for your liver to process certain medications. Your body will likely react to them differently than expected. For example, a normal medication dose for someone else could end up causing excessive side effects for you. This is one of the main reasons why you and your healthcare provider may decide to make changes to your medication regimen.
What is a CYP enzyme?
Liver enzymes are also known as cytochrome P450 (CYP) enzymes. Your liver makes several CYP enzymes, and they each have a goal of metabolizing medications when needed.
Many — but not all — medications are processed by one or more CYP enzymes. If your liver isn’t working as well as it could, these enzymes may be more or less effective.
What’s more, if you take multiple medications that work with the same enzyme, you may experience unwanted side effects. This is the culprit for many drug interactions. Some medications block the effects of CYP enzymes, while others make them too efficient. You might also eat certain foods that affect different liver enzymes.
How are medication dosages adjusted for people with liver problems?
If you have liver problems, you’ll likely need less medication compared to other people. You may be told to take a lower dose or to take your medication less often. This will help prevent additional side effects, but it shouldn’t interfere with your medication’s effectiveness.
But how do you know if you have liver problems in the first place? Your healthcare provider can perform blood tests — called liver function tests (LFTs) — to check your liver health. The results help your provider decide whether or not your medication dosage needs to be adjusted. They may want to run these tests before you start taking a medication and repeat them throughout your treatment.
Examples of medications that are adjusted based on liver status
Several medications should be adjusted if you have liver problems. Some should be avoided altogether. Your provider can talk to you about medications and dosages that could be unsafe for you. Examples include:
Acetaminophen (Tylenol)
Amiodarone (Pacerone)
Carbamazepine (Tegretol)
Fluoxetine (Prozac)
Lorazepam (Ativan)
Omeprazole (Prilosec)
Rosuvastatin (Crestor)
Warfarin (Coumadin, Jantoven)
However, not all medications are metabolized by the liver. Dosage adjustments might not be necessary for some of the medications you take. Your pharmacist can tell you more about the effects of liver disease on drug metabolism.
How are liver function tests used for accurate medication dosing?
LFT results help your healthcare provider understand how healthy your liver is. They’re a common way to gauge if you’ll need any medication dosage changes. Some providers refer to them as a “liver panel.”
LFTs check for signs of liver damage by measuring specific proteins in your bloodstream. They monitor your blood levels of AST (aspartate transaminase), ALT (alanine aminotransferase), albumin, and other proteins that are associated with your liver health. These proteins are not the same as CYP enzymes, but they can help predict changes in drug metabolism. If there are too few or too many liver proteins in your blood, this could be a sign of liver damage.
Medications that are adjusted for liver problems are based on the severity of potential liver damage. Your provider may classify the severity of your liver problems using a system known as the “Child-Pugh” scoring system. This system uses LFT results to classify your liver damage on a scale ranging from mild to severe.
If you have “mild” liver impairment, you may not need any adjustments at all. Your healthcare provider may just recommend extra monitoring to watch out for any side effects. But if your liver impairment is considered “moderate” or “severe,” you may be told to take a lower dose. Still, this all depends on the medication. Different medications have different recommendations.
What happens if my medication isn’t adjusted for liver impairment?
If you have liver impairment, normal medication dosages might be harmful to your body. That’s why it’s important to take a lower, adjusted dose in certain scenarios. When liver-dependent medications aren’t adjusted, you’re more likely to have side effects.
You and your healthcare provider can discuss the possible side effects of your medication and make a plan to prevent them. You might also notice increasing symptoms of liver damage if your medications are not adjusted, such as:
Dark urine
Yellow coloration of the eyes or skin (jaundice)
Pain in the upper right portion of your gut
General itching
If you think you’re experiencing new or worsening liver damage, talk to your healthcare provider about your symptoms and medications as soon as you can.
The bottom line
Your liver is the primary organ involved in drug metabolism. If you have liver damage, some medications may not work as expected. Some medications can also be harmful for your body. Your provider will help you decide the medication dosages that will be safe and work best for you.
Why trust our experts?
References
American Liver Foundation. (n.d.). Liver diseases.
American Liver Foundation. (n.d.) Viral hepatitis.
American Liver Foundation. (2022). The healthy liver.
Duthaler, U., et al. (2022). Liver cirrhosis affects the pharmacokinetics of the six substrates of the Basel phenotyping cocktail differently. Clinical Pharmacokinetics.
Garza, A. Z., et al. (2022). Drug elimination. StatPearls.
Likhitsup, A., et al (2022). Medications and the liver. American College of Gastroenterology.
National Library of Medicine. (2023). LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. National Center for Biotechnology Information.
Tsoris, A., et al. (2023). Use of the Child Pugh score in liver disease. StatPearls.
