Diclofenac (Diclofenac sodium) — Patient Information for the UK

Diclofenac (often listed as diclofenac sodium) is a well-known anti-inflammatory medicine used to relieve pain and reduce inflammation. It belongs to a group called non-steroidal anti-inflammatory drugs (NSAIDs). In the UK, diclofenac is available in different forms, including tablets and gels/creams, depending on strength and local regulations.

This guide is written to help you understand what diclofenac does, how it works in the body, how it’s typically used, and what to watch out for—especially regarding stomach, heart, kidney and drug interactions.

1) Basic product information

Note: Product names, strengths and dosing schedules differ between brands and formulations. Always check the specific label or package leaflet for your exact product.

2) How diclofenac works (mechanism of action)

Diclofenac reduces pain, swelling (inflammation), and stiffness by blocking the activity of enzymes called COX-1 and COX-2 (cyclo-oxygenase enzymes). These enzymes help the body make prostaglandins, chemicals involved in pain signalling, fever, and inflammation.

By reducing prostaglandins, diclofenac:

• decreases inflammation in affected tissues
• reduces pain sensitivity
• can lower pain-related swelling and stiffness, particularly in joints

3) Pharmacokinetics — what happens in the body

Pharmacokinetics describes how the medicine is absorbed, distributed, metabolised and eliminated.

• Absorption: Oral diclofenac is absorbed through the gastrointestinal tract. Topical diclofenac gel is absorbed through the skin in smaller systemic amounts compared with oral forms.
• Distribution: Diclofenac distributes into tissues including joints. Binding to blood proteins is significant.
• Metabolism: The medicine is metabolised mainly in the liver.
• Elimination: Diclofenac and its metabolites are cleared largely via the kidneys (and to some extent via the bile).
• Half-life: Diclofenac’s elimination half-life is typically around 1–2 hours for immediate-release oral forms, though this can vary by formulation and individual factors.

Topical vs oral: With topical products, systemic exposure is lower, but interactions can still occur—especially if used over large areas or with prolonged use.

4) What diclofenac is used for (typical use)

Diclofenac is commonly used for conditions where inflammation and pain play a major role. Typical indications include:

• Muscle and joint pain (e.g., sprains, strains)
• Back pain and soft tissue inflammation (where appropriate)
• Osteoarthritis pain and stiffness (topical may be used for certain limb joints)
• Rheumatoid arthritis symptoms (oral use under clinician guidance)
• Acute pain with inflammation (depending on product form and strength)

Topical diclofenac gel is frequently used for localised pain in joints such as:

• hands and fingers
• knees
• ankles and feet

Important: Diclofenac helps relieve symptoms but does not cure the underlying cause of chronic conditions.

5) Timing — when to take it and how long to use

Timing depends on the formulation and the reason you’re using it.

• Oral diclofenac: Often taken with water, and dosing schedules vary (commonly multiple times daily for certain immediate-release products; sustained-release products have different schedules).
• Topical diclofenac: Applied to the affected area at set intervals (commonly a few times daily depending on strength/product).

General practical principle: Use the lowest effective dose for the shortest duration needed to control symptoms, unless your healthcare professional advises otherwise.

If symptoms persist: Seek medical advice if pain does not improve or if it worsens after a short trial, especially for injuries or flare-ups.

6) Food interactions and stomach protection

Oral diclofenac can irritate the stomach and increase the risk of ulcers or bleeding. Taking it with food or soon after a meal can reduce stomach irritation for some people.

• Take with food if your product instructions allow and you experience indigestion.
• Avoid taking it on an empty stomach if you’re prone to stomach upset.
• Do not crush or split tablets unless the product instructions permit (especially for modified-release forms).

Topical diclofenac is less affected by food because systemic absorption is lower. Still, if you use oral NSAIDs as well, food-related stomach risk remains relevant.

7) Alcohol and medicine interactions

Combining diclofenac with alcohol can increase the risk of stomach irritation, ulcers and bleeding. Alcohol can also worsen drowsiness or dizziness if you experience these side effects.

• Try to avoid alcohol while taking diclofenac, or keep it to a minimum.
• If you drink regularly or have a history of stomach ulcers, seek advice before using diclofenac.

Common medicine interactions include:

• Other NSAIDs (e.g., ibuprofen, naproxen, aspirin for pain): increases risk of stomach bleeding and kidney strain. Avoid double-dosing.
• Blood thinners (e.g., warfarin, apixaban, rivaroxaban, dabigatran): increases bleeding risk.
• Antiplatelet medicines (e.g., clopidogrel, low-dose aspirin): may increase bleeding risk.
• Corticosteroids (e.g., prednisolone): higher risk of gastrointestinal bleeding.
• Selective serotonin reuptake inhibitors (SSRIs) (e.g., sertraline, fluoxetine) and other antidepressants that affect serotonin: may increase bleeding risk.
• Diuretics (water tablets) and ACE inhibitors/ARBs (e.g., ramipril, lisinopril, losartan): can affect kidney function when combined with NSAIDs (the “triple whammy” concept when NSAID + diuretic + ACEi/ARB occurs).
• Lithium: NSAIDs may increase lithium levels (toxicity risk).
• Methotrexate: NSAIDs can increase methotrexate levels (toxicity risk), especially at higher doses.
• Digoxin: NSAIDs can raise digoxin levels in some cases.
• Anti-diabetic medicines: NSAIDs can affect blood sugar control in some individuals.

Always check your full medication list (including over-the-counter products) to avoid duplication of NSAIDs.

8) Indications — when diclofenac may be appropriate

Within the UK, diclofenac products are used for musculoskeletal pain and inflammatory conditions. Indications depend on the specific product, strength, and route of administration:

• Topical diclofenac: commonly used for localised osteoarthritis pain (particularly joints in the limbs) and soft tissue injuries where local treatment is suitable.
• Oral diclofenac: used for more widespread inflammatory pain under appropriate safety screening.

Not suitable for everyone: If you have certain medical conditions—particularly a history of stomach ulcers/bleeding, significant heart disease, severe kidney impairment, or aspirin/NSAID allergy—diclofenac may be unsuitable or require close guidance.

9) Dosing — general guidance for common forms

Dose depends on:

• the formulation (oral vs topical, strength, and whether immediate-release or modified-release)
• age and individual risk factors
• the condition being treated

Because exact dosing differs by product, always follow the instructions on your pack or the product leaflet. The information below provides general principles rather than a personal prescription.

Oral diclofenac (general principles)

• Use the lowest effective dose.
• Take with food if your stomach is sensitive.
• Do not exceed the maximum daily dose stated for your specific product.

Topical diclofenac gel (general principles)

• Apply only to the affected area and avoid broken skin.
• Wash hands after application unless treating the hands.
• Do not cover with tight dressings unless instructed.
• Avoid applying heat packs on top of the treated area unless advised, as this may increase absorption.

Children and adolescents: Age-appropriate dosing depends on the product and regulatory status. Use only if specifically permitted for the age group and follow the label strictly.

10) Safety profile — who should take extra care

Like all NSAIDs, diclofenac can cause side effects. Many are mild, but some—particularly involving the stomach, heart or kidneys—can be serious.

Common side effects

• indigestion, heartburn, nausea
• stomach discomfort
• headache, dizziness
• for topical products: skin irritation, redness, itching or a rash at the application site

Serious risks (seek urgent help if these occur)

• Signs of stomach bleeding: vomiting blood or material like “coffee grounds,” black/tarry stools, unexplained severe abdominal pain
• Allergic reaction: swelling of face/lips, wheezing, severe rash, or trouble breathing
• Chest pain, shortness of breath, weakness on one side of the body (possible cardiovascular or clot-related events)
• Reduced urination or sudden fluid retention (possible kidney problems)
• Severe skin reactions (rare but serious), including blistering or peeling

Who should be especially cautious

• People with a history of peptic ulcers or gastrointestinal bleeding
• People with known heart disease or prior stroke (NSAIDs may increase cardiovascular risk)
• Those with kidney disease, dehydration, or elderly patients (higher risk of kidney effects)
• People with asthma that worsens with aspirin/NSAIDs
• Those taking medicines that affect bleeding risk (e.g., anticoagulants, antiplatelets)
• People using multiple NSAIDs concurrently

Topical caution: Even with gels, avoid using on large areas for long periods if you’re at higher risk. If you develop a significant rash or burning, stop and seek advice.

11) Practical use tips (how to get the most benefit with the least risk)

• Check your medicines: Look for NSAIDs in combination products (e.g., cold/flu remedies) to avoid accidental duplication.
• Use correct application technique for topical gel: measure the amount and apply as directed.
• Track response: If your pain isn’t improving after a short period, consider whether another approach is needed.
• Consider non-drug options alongside diclofenac: gentle movement, heat/cold therapy, stretching, and physiotherapy can improve outcomes for musculoskeletal issues.
• Stay hydrated (especially if you’re older or have kidney-related concerns).
• Do not “double up”: Avoid taking oral and topical diclofenac together without guidance, and avoid combining with other NSAIDs.

12) Alternative options for pain and inflammation

Depending on your condition, alternatives may include:

• Paracetamol (acetaminophen): may help pain, but it doesn’t reduce inflammation as effectively as NSAIDs.
• Other topical NSAIDs: such as ibuprofen-based gels (where available) for localised pain.
• Different NSAIDs: some people may tolerate another NSAID better; however, class risks can overlap.
• Non-NSAID anti-inflammatory approaches: physical therapy, splints/braces, activity modification, and strengthening exercises.
• For certain conditions: clinicians may consider other treatments tailored to the cause (e.g., gout management, inflammatory arthritis therapies).

Choosing alternatives: Your best option depends on your medical history and the type of pain (inflammatory vs mechanical, localised vs widespread).

13) Market and legal context in the UK

In the UK, medicine availability is governed by regulatory frameworks set by bodies such as the Medicines and Healthcare products Regulatory Agency (MHRA), and guidance regarding supply and classification for different strengths and formulations. Products may be:

• available over the counter in certain strengths/forms, or
• available via pharmacy supply with checks, or
• classified for prescriber-led use depending on formulation and dose.

Because diclofenac has recognized risks, especially for the stomach and cardiovascular system, UK product information and prescribing/supply guidance generally emphasise:

• using the lowest effective dose
• shortest duration of use
• careful screening for contraindications and interaction potential

Always follow the specific instructions for your product, as the legal category and recommended use can differ by brand and strength.

14) Recent guidance and safety updates (UK context)

Over recent years, UK and EU safety communications and clinical guidance have continued to focus on NSAID safety. Key themes include:

• Cardiovascular risk awareness: NSAIDs, including diclofenac, may increase risk of cardiovascular events, particularly with higher doses and longer use.
• Gastrointestinal protection: risk increases in people with prior ulcers or bleeding, older age, and when used with interacting medicines (e.g., steroids or anticoagulants).
• Kidney function considerations: dehydration, existing kidney disease, and certain combination medicines can increase risk.
• Avoiding inappropriate combination: patients are encouraged not to combine NSAIDs unless a clinician has advised it.

If you have concerns about your personal risk, speak to a pharmacist for product suitability and safer alternatives.

15) Delivery and availability in the UK

Availability of diclofenac varies by formulation and strength. Many online pharmacies in the UK offer delivery of appropriate products where permitted by law and supply rules.

• Check the product page: confirm the exact formulation (oral vs topical), strength, and pack size.
• Delivery times: depend on your location and the courier used. Typical delivery windows may be shown during checkout.
• Packaging: medicines are usually dispatched in tamper-evident packaging with clear labelling.
• Stock status: availability can change—look for “in stock” or estimated dispatch information.

Storage: Follow the storage instructions on the pack. Many medicines should be stored at room temperature and kept out of reach of children.

16) FAQ — Frequently asked questions

Is diclofenac safe for everyone?

No. Diclofenac is not suitable for everyone. It may be unsafe if you have a history of stomach ulcers/bleeding, NSAID allergy, certain heart conditions, kidney disease, or asthma worsened by NSAIDs. If you’re unsure, speak to a pharmacist and check the product leaflet for contraindications.

Can I take diclofenac with other painkillers?

It depends which one. Avoid combining diclofenac with other NSAIDs (such as ibuprofen or naproxen). Paracetamol is generally considered a safer pairing for pain relief for many people, but check your specific product guidance and any medical conditions you have.

Should I take diclofenac with food?

For many people taking oral diclofenac, taking it with food helps reduce stomach irritation. Follow your product’s instructions and consider eating a meal or snack if your stomach is sensitive.

What if I miss a dose?

Take it when you remember unless it’s close to the time for your next dose. Do not take extra to make up for a missed dose. For topical products, apply only the recommended amount at the scheduled intervals.

How quickly does diclofenac work?

Many people notice pain relief within hours. Topical gel may improve symptoms gradually over the first few days. If there is no improvement after a short period (or if symptoms worsen), seek advice.

Can I drink alcohol while using diclofenac?

It’s best to avoid alcohol or keep it minimal. Alcohol can increase the risk of stomach irritation and bleeding with NSAIDs.

Are there interactions with blood thinners?

Yes. Diclofenac can increase bleeding risk when used with anticoagulants or antiplatelet medicines. If you take these medicines, check with a pharmacist before using diclofenac.

Can I use diclofenac gel on broken skin?

No. Avoid applying to broken, infected or irritated skin. If you get significant rash or irritation, stop and seek advice.

How long can I use topical diclofenac?

Follow the instructions for your specific product. As a general safety approach, use the lowest effective amount for the shortest time needed.

What should I do if I experience serious side effects?

Stop using the medicine and seek urgent medical help if you notice signs of bleeding, allergic reaction, chest pain, severe breathlessness, sudden weakness, or severe skin reactions.

Summary

Diclofenac (diclofenac sodium) is an NSAID used in the UK to relieve pain and inflammation, especially for musculoskeletal conditions like joint pain and soft tissue injuries. It works by reducing prostaglandins through COX enzyme inhibition. While it can be effective, it has potential risks—including stomach bleeding, kidney effects and cardiovascular concerns—particularly for people with existing risk factors or when combined with interacting medicines.

To use diclofenac safely, follow product instructions carefully, avoid duplication with other NSAIDs, use the lowest effective dose for the shortest period, and be alert for warning signs. If you have any doubts about suitability or interactions, a pharmacist can help you choose the most appropriate option.