Can You Take Lithium and Diclofenac Together? What You Need to Know About This Interaction

Lithium and diclofenac are documented to interact at a moderate severity level, and patients using both medications together require careful monitoring for signs of lithium toxicity. While the combination is not absolutely contraindicated, healthcare providers consider this a clinically significant pairing that demands watchfulness and regular communication between you and your medical team.

What the Source Says

According to drug labeling information reviewed by the National Library of Medicine, the interaction between diclofenac (a nonsteroidal anti-inflammatory drug, or NSAID) and lithium is classified as moderate in severity. The source record directs healthcare providers to monitor patients for signs of lithium toxicity during concomitant use. This means that when these two drugs are taken together, there is a recognized risk that lithium levels in your bloodstream could rise to harmful levels, and your healthcare team needs to watch for that possibility.

The interaction source comes from NLP (natural language processing) analysis of diclofenac drug labeling, updated as of May 2026. This reflects current FDA-reviewed pharmaceutical information.

How to Understand This

To make sense of this interaction, it helps to know what each drug does and why they might affect one another.

What is lithium? Lithium is a medication used primarily to treat bipolar disorder and certain types of depression. It works by affecting neurotransmitter activity in the brain. Lithium has a narrow therapeutic window, meaning the difference between a helpful dose and a toxic dose is relatively small. Your body excretes (eliminates) lithium mainly through the kidneys, and maintaining the right blood level of lithium is crucial to both its effectiveness and safety.

What is diclofenac? Diclofenac is an NSAID—a class of pain-relieving and anti-inflammatory drugs. Common NSAIDs include ibuprofen and naproxen. Diclofenac is often used for moderate pain, arthritis, and inflammatory conditions.

Why might they interact? The source record does not specify a documented mechanism for this interaction. However, general pharmacology knowledge shows that NSAIDs can affect how the kidneys handle various substances, including lithium. When kidney function is altered by an NSAID, lithium excretion may be reduced, potentially causing lithium to accumulate in the body to higher-than-intended levels. This accumulation is the basis for monitoring concern. That said, the absence of a mechanism statement in the source record means we cannot point to a single, well-defined pathway that has been formally documented for the lithium-diclofenac pair. The interaction itself is documented; the precise mechanism is not specified in the labeling information reviewed here.

What is lithium toxicity? Lithium toxicity ranges from mild to severe. Early signs can include tremor, nausea, vomiting, diarrhea, confusion, and slurred speech. More serious toxicity can affect the heart rhythm and kidneys. This is why monitoring is essential: catching a rising lithium level before symptoms appear allows for dose adjustment or medication change before harm occurs.

Who Should Pay Particular Attention

While any patient taking both lithium and diclofenac together should be aware of this interaction, certain situations warrant heightened attention:

• Patients new to diclofenac: If you have been stable on lithium for a long time and your healthcare provider starts you on diclofenac, this is a time to alert your provider and pharmacist to the documented interaction so they can arrange appropriate monitoring.
• Patients with kidney concerns: Since lithium excretion depends on kidney function, people with any history of kidney disease or reduced kidney function should make sure their healthcare team knows about both medications and any baseline kidney concerns.
• Patients on higher lithium doses: Those requiring higher therapeutic doses of lithium may have less room for levels to rise before approaching toxic thresholds.
• Older adults: Age-related changes in kidney function mean that older patients may be at relatively higher risk for lithium accumulation.

Hypothetical Examples

Hypothetical scenario 1: A 45-year-old person with bipolar disorder has been taking lithium 900 mg daily for two years with stable mood and normal lithium blood levels. They develop osteoarthritis pain in their knee and their physician prescribes diclofenac 50 mg twice daily. Because of the documented interaction, the physician orders a lithium blood level check two to three weeks after starting diclofenac. The check reveals that the lithium level has risen by 20%, still within acceptable range but trending upward. The physician and patient discuss this result: they might reduce the lithium dose slightly, increase the frequency of monitoring, or try a different pain reliever. This is the monitoring process at work.

Hypothetical scenario 2: A different patient takes lithium and begins diclofenac but does not inform their prescriber or pharmacist that they are on lithium, or the prescriber forgets to check the drug interaction. Over several weeks, the patient notices increasing tremor, mild nausea, and difficulty concentrating. A lithium blood level check reveals toxic levels. Had the interaction been flagged and monitored proactively, the rising level could have been detected and managed before symptoms appeared. This illustrates why transparency and communication are critical.

What to Discuss With a Pharmacist or Physician

If you take lithium and need pain relief or anti-inflammatory medication, or if you take diclofenac and have been prescribed lithium, here are questions and topics to raise:

• "I take lithium and have been prescribed diclofenac. I understand these interact. What monitoring do you recommend?" This opens a conversation about baseline lithium levels, when follow-up checks should occur, and what symptoms to watch for.
• "Are there alternative pain relievers I could use instead of an NSAID?" Some patients can use acetaminophen or other non-NSAID options. Your healthcare provider can advise whether that is safe for your condition.
• "What are the early warning signs of lithium toxicity I should know about?" Understanding tremor, nausea, confusion, and other early signals helps you recognize a problem quickly.
• "How often should my lithium level be checked if I take diclofenac?" Monitoring schedules vary; your provider will determine what is appropriate for your situation.
• "If I need to continue diclofenac, does my lithium dose need to be adjusted?" Sometimes doses are adjusted preemptively; sometimes the team waits to see what monitoring shows.
• "What should I do if I develop symptoms like severe tremor, confusion, or irregular heartbeat?" Know when to seek immediate care versus scheduling a routine follow-up appointment.

Do not start, stop, skip, or change either medication on your own. All decisions about managing this pair should be made with your prescribing physician and pharmacy team.

Key Takeaways

• Lithium and diclofenac have a documented moderate-severity interaction that requires monitoring for lithium toxicity.
• The source record directs healthcare providers to monitor for signs of lithium toxicity when these drugs are used together, but does not specify a detailed mechanism in the labeling material reviewed.
• Lithium has a narrow therapeutic window, and NSAIDs like diclofenac may affect kidney handling of lithium, potentially raising blood levels.
• Monitoring typically involves baseline and follow-up lithium blood level checks, symptom awareness, and regular communication with your healthcare team.
• Do not change or stop either medication without consulting your physician and pharmacist. They can decide whether the combination is appropriate for you, what monitoring is needed, and whether alternatives exist.

Sources

• DailyMed—National Library of Medicine Drug Information: Central repository of FDA-reviewed drug labeling
• RxNorm—NLM UMLS Normalized Drug Nomenclature: Authoritative drug naming and classification
• OpenFDA—FDA Public Data and APIs: FDA-curated drug safety information
• PubMed—National Center for Biotechnology Information: Biomedical literature search (for deeper background on lithium and NSAID pharmacology)

Ready to check your medications for interactions? Visit checkdruginteractions.com to search your complete medication list and get a personalized report. Always confirm any medication questions or changes with your pharmacist or physician—they have your full medical history and can give you guidance tailored to your specific situation.