Safety reference
Check supplement and drug interactions before you combine.
Select a supplement and a medication to check for known interactions. Severity ratings range from mild timing adjustments to combinations that require immediate veterinary guidance.
Medical disclaimer: This tool provides general information based on published pharmacology data. It is not a substitute for veterinary advice. Always consult your veterinarian before combining supplements with prescribed medications. Do not stop prescribed medications based on this tool.
Check a specific combination
Severity levels
All documented interactions
Browse all 15 supplement-drug interaction pairs in our database.
| Supplement | Drug / Medication | Severity | Description | Guidance |
|---|---|---|---|---|
| Fish Oil (Omega-3) | NSAIDs (Carprofen, Meloxicam) | Moderate | Both omega-3 fatty acids and NSAIDs have anti-platelet effects. Combined use may increase bleeding risk, particularly during surgery or in dogs with clotting disorders. | Monitor for unusual bruising or prolonged bleeding. Inform your veterinarian before any surgical procedure. Consider reducing fish oil dose 5-7 days before planned surgery. |
| Fish Oil (Omega-3) | Blood Thinners (Warfarin, Heparin) | Serious | Omega-3 fatty acids inhibit platelet aggregation. When combined with anticoagulants, the risk of hemorrhage increases significantly. | Use only under direct veterinary supervision. More frequent coagulation monitoring (PT/INR) is required. Dose adjustment of the anticoagulant may be necessary. |
| Glucosamine | Diabetes Medications (Insulin, Glipizide) | Mild | Glucosamine may theoretically affect glucose metabolism, potentially reducing insulin sensitivity. Clinical significance in dogs is debated. | Monitor blood glucose more frequently when starting glucosamine. Adjust diabetes medication if glucose trends upward. Effect is generally small. |
| Milk Thistle (Silymarin) | Chemotherapy Drugs | Moderate | Silymarin can inhibit cytochrome P450 enzymes (CYP3A4, CYP2C9), potentially altering the metabolism and efficacy of chemotherapy agents. | Discuss timing and dosing with your veterinary oncologist. Some oncologists support concurrent use for hepatoprotection; others advise separation by several hours. |
| SAMe | Antidepressants (SSRIs, Tricyclics) | Serious | SAMe increases serotonin levels. Combined with serotonergic drugs (fluoxetine, clomipramine), there is a risk of serotonin syndrome, which can cause tremors, hyperthermia, and seizures. | Do not combine without veterinary oversight. If both are needed, introduce one at a time with close monitoring. Serotonin syndrome requires emergency treatment. |
| Probiotics | Antibiotics | Mild | Antibiotics reduce the viability of probiotic organisms. Taking them simultaneously reduces the probiotic benefit, though no safety concern exists. | Separate administration by at least 2 hours. Give probiotics between antibiotic doses or continue for 2-4 weeks after the antibiotic course ends to restore gut flora. |
| Turmeric / Curcumin | NSAIDs (Carprofen, Meloxicam) | Mild | Both have anti-inflammatory properties. Combined use may produce additive effects, which could increase GI irritation risk in sensitive dogs. | Monitor for GI signs (vomiting, soft stool, reduced appetite). Consider using one or the other rather than both simultaneously. Inform your vet about concurrent use. |
| Iron Supplements | Thyroid Medications (Levothyroxine) | Moderate | Iron chelates levothyroxine in the GI tract, reducing its absorption by up to 50-70%. This can result in inadequate thyroid hormone levels. | Separate administration by at least 4 hours. Give levothyroxine on an empty stomach in the morning; give iron supplements with a later meal. Recheck thyroid levels after starting iron. |
| Calcium Supplements | Fluoroquinolone Antibiotics (Enrofloxacin) | Moderate | Calcium ions form insoluble complexes with fluoroquinolone antibiotics, reducing absorption and potentially rendering the antibiotic ineffective. | Separate by at least 2 hours (ideally 4). This applies to all calcium-containing products including dairy and calcium-rich chews. |
| Vitamin E | Blood Thinners (Warfarin, Heparin) | Moderate | High-dose vitamin E has mild anticoagulant properties and may potentiate the effect of warfarin, increasing bleeding risk. | Use only at recommended doses (not megadoses). Monitor coagulation parameters if combining. Discuss with your vet before starting vitamin E in dogs on anticoagulant therapy. |
| CBD (Cannabidiol) | Liver-Metabolized Drugs (Phenobarbital, Ketoconazole) | Moderate | CBD inhibits several cytochrome P450 enzymes, particularly CYP2D6 and CYP3A4. This can increase blood levels of drugs metabolized by the liver, raising toxicity risk. | If using CBD with liver-metabolized medications, start with a low CBD dose and monitor for adverse effects. Liver enzyme panels may be warranted. Inform your vet about all supplements. |
| Melatonin | Sedatives (Acepromazine, Trazodone) | Mild | Both melatonin and sedatives have calming effects. Combined use may cause excessive sedation, lethargy, or ataxia. | Reduce the dose of one or both when combining. Monitor for excessive drowsiness, stumbling, or difficulty waking. Start with the lowest effective dose of each. |
| Potassium Supplements | ACE Inhibitors (Enalapril, Benazepril) | Serious | ACE inhibitors reduce potassium excretion by the kidneys. Adding potassium supplements can cause dangerous hyperkalemia (elevated blood potassium), leading to cardiac arrhythmias. | Do not supplement potassium unless directed by a veterinarian with electrolyte monitoring. Signs of hyperkalemia include muscle weakness, slow heart rate, and collapse. This is a veterinary emergency. |
| Fiber Supplements (Psyllium, Pumpkin) | Any Oral Medication | Mild | Fiber can bind to medications in the GI tract, slowing or reducing their absorption. This is a physical interaction, not a chemical one. | Separate fiber supplements from medications by at least 1 hour. Give medications first on an empty stomach when possible, then provide fiber with a later meal. |
| Grapefruit Extract | CYP3A4-Metabolized Drugs (Cyclosporine, many others) | Serious | Grapefruit compounds (furanocoumarins) potently inhibit CYP3A4, an enzyme responsible for metabolizing many drugs. This can dramatically increase drug blood levels and toxicity risk. | Avoid this combination entirely unless under strict veterinary supervision. Cyclosporine levels, in particular, can increase 2-3x with concurrent grapefruit. Many veterinary drugs are CYP3A4 substrates. |
Fish Oil (Omega-3)
+ NSAIDs (Carprofen, Meloxicam)
Both omega-3 fatty acids and NSAIDs have anti-platelet effects. Combined use may increase bleeding risk, particularly during surgery or in dogs with clotting disorders.
Guidance
Monitor for unusual bruising or prolonged bleeding. Inform your veterinarian before any surgical procedure. Consider reducing fish oil dose 5-7 days before planned surgery.
Fish Oil (Omega-3)
+ Blood Thinners (Warfarin, Heparin)
Omega-3 fatty acids inhibit platelet aggregation. When combined with anticoagulants, the risk of hemorrhage increases significantly.
Guidance
Use only under direct veterinary supervision. More frequent coagulation monitoring (PT/INR) is required. Dose adjustment of the anticoagulant may be necessary.
Glucosamine
+ Diabetes Medications (Insulin, Glipizide)
Glucosamine may theoretically affect glucose metabolism, potentially reducing insulin sensitivity. Clinical significance in dogs is debated.
Guidance
Monitor blood glucose more frequently when starting glucosamine. Adjust diabetes medication if glucose trends upward. Effect is generally small.
Milk Thistle (Silymarin)
+ Chemotherapy Drugs
Silymarin can inhibit cytochrome P450 enzymes (CYP3A4, CYP2C9), potentially altering the metabolism and efficacy of chemotherapy agents.
Guidance
Discuss timing and dosing with your veterinary oncologist. Some oncologists support concurrent use for hepatoprotection; others advise separation by several hours.
SAMe
+ Antidepressants (SSRIs, Tricyclics)
SAMe increases serotonin levels. Combined with serotonergic drugs (fluoxetine, clomipramine), there is a risk of serotonin syndrome, which can cause tremors, hyperthermia, and seizures.
Guidance
Do not combine without veterinary oversight. If both are needed, introduce one at a time with close monitoring. Serotonin syndrome requires emergency treatment.
Probiotics
+ Antibiotics
Antibiotics reduce the viability of probiotic organisms. Taking them simultaneously reduces the probiotic benefit, though no safety concern exists.
Guidance
Separate administration by at least 2 hours. Give probiotics between antibiotic doses or continue for 2-4 weeks after the antibiotic course ends to restore gut flora.
Turmeric / Curcumin
+ NSAIDs (Carprofen, Meloxicam)
Both have anti-inflammatory properties. Combined use may produce additive effects, which could increase GI irritation risk in sensitive dogs.
Guidance
Monitor for GI signs (vomiting, soft stool, reduced appetite). Consider using one or the other rather than both simultaneously. Inform your vet about concurrent use.
Iron Supplements
+ Thyroid Medications (Levothyroxine)
Iron chelates levothyroxine in the GI tract, reducing its absorption by up to 50-70%. This can result in inadequate thyroid hormone levels.
Guidance
Separate administration by at least 4 hours. Give levothyroxine on an empty stomach in the morning; give iron supplements with a later meal. Recheck thyroid levels after starting iron.
Calcium Supplements
+ Fluoroquinolone Antibiotics (Enrofloxacin)
Calcium ions form insoluble complexes with fluoroquinolone antibiotics, reducing absorption and potentially rendering the antibiotic ineffective.
Guidance
Separate by at least 2 hours (ideally 4). This applies to all calcium-containing products including dairy and calcium-rich chews.
Vitamin E
+ Blood Thinners (Warfarin, Heparin)
High-dose vitamin E has mild anticoagulant properties and may potentiate the effect of warfarin, increasing bleeding risk.
Guidance
Use only at recommended doses (not megadoses). Monitor coagulation parameters if combining. Discuss with your vet before starting vitamin E in dogs on anticoagulant therapy.
CBD (Cannabidiol)
+ Liver-Metabolized Drugs (Phenobarbital, Ketoconazole)
CBD inhibits several cytochrome P450 enzymes, particularly CYP2D6 and CYP3A4. This can increase blood levels of drugs metabolized by the liver, raising toxicity risk.
Guidance
If using CBD with liver-metabolized medications, start with a low CBD dose and monitor for adverse effects. Liver enzyme panels may be warranted. Inform your vet about all supplements.
Melatonin
+ Sedatives (Acepromazine, Trazodone)
Both melatonin and sedatives have calming effects. Combined use may cause excessive sedation, lethargy, or ataxia.
Guidance
Reduce the dose of one or both when combining. Monitor for excessive drowsiness, stumbling, or difficulty waking. Start with the lowest effective dose of each.
Potassium Supplements
+ ACE Inhibitors (Enalapril, Benazepril)
ACE inhibitors reduce potassium excretion by the kidneys. Adding potassium supplements can cause dangerous hyperkalemia (elevated blood potassium), leading to cardiac arrhythmias.
Guidance
Do not supplement potassium unless directed by a veterinarian with electrolyte monitoring. Signs of hyperkalemia include muscle weakness, slow heart rate, and collapse. This is a veterinary emergency.
Fiber Supplements (Psyllium, Pumpkin)
+ Any Oral Medication
Fiber can bind to medications in the GI tract, slowing or reducing their absorption. This is a physical interaction, not a chemical one.
Guidance
Separate fiber supplements from medications by at least 1 hour. Give medications first on an empty stomach when possible, then provide fiber with a later meal.
Grapefruit Extract
+ CYP3A4-Metabolized Drugs (Cyclosporine, many others)
Grapefruit compounds (furanocoumarins) potently inhibit CYP3A4, an enzyme responsible for metabolizing many drugs. This can dramatically increase drug blood levels and toxicity risk.
Guidance
Avoid this combination entirely unless under strict veterinary supervision. Cyclosporine levels, in particular, can increase 2-3x with concurrent grapefruit. Many veterinary drugs are CYP3A4 substrates.
Frequently asked questions
How reliable is this interaction data?
Interactions listed here are based on published veterinary pharmacology references, known drug metabolism pathways, and documented case reports. However, interaction severity can vary based on individual dog factors including breed, liver function, kidney function, and concurrent health conditions. This tool provides general guidance, not definitive safety assessments.
What should I do if my dog is taking a combination listed as "serious"?
Do not stop any prescribed medication without consulting your veterinarian. Contact your vet to discuss the interaction, potential dose adjustments, monitoring requirements, or alternative supplement options. Serious interactions require professional management, not self-adjustment.
My supplement and drug combination is not listed. Does that mean it is safe?
Not necessarily. This database covers the most commonly encountered interactions. The absence of a listing means we have not identified a documented interaction, but novel or rare interactions may exist. Always inform your veterinarian about all supplements your dog takes.
Can timing of administration eliminate the interaction risk?
For absorption-based interactions (e.g., calcium + antibiotics, fiber + medications), separating doses by the recommended time window can significantly reduce the interaction. For metabolic interactions (e.g., CBD + liver-metabolized drugs), timing alone does not eliminate the risk because both compounds are processed by the same liver enzymes regardless of when they are taken.
Are these interactions specific to dogs?
Yes, we focus on canine-relevant interactions. Some interaction data is extrapolated from human pharmacology when veterinary-specific studies are unavailable, but dosing guidance and severity assessments account for known species differences in drug metabolism.
This interaction database is for informational purposes only and does not constitute veterinary or medical advice. Interaction data is compiled from published veterinary pharmacology references, drug metabolism pathway analyses, and documented case reports. Individual responses may vary. Never adjust prescribed medications without consulting your veterinarian. If you suspect an adverse interaction, contact your veterinarian or an emergency veterinary clinic immediately.