Is it safe to take copper supplements with vitamin C (ascorbic acid)?

Safety of Taking Copper Supplements with Vitamin C

Taking copper supplements together with vitamin C (ascorbic acid) is not safe and should be avoided, as this combination induces systemic oxidative stress and can cause organ damage, particularly kidney injury. 1

The Fundamental Problem: Fenton Reaction

When vitamin C and copper are combined, they undergo a Fenton reaction that generates highly reactive hydroxyl radicals—among the most damaging free radicals in biological systems. 1, 2

Key evidence from the highest quality recent study:

• A 2023 experimental study demonstrated that combined administration of vitamin C plus copper resulted in:

  • Elevated protein oxidation throughout the body (serum, intestine, bladder, kidney) 1
  • Significant loss of kidney function with increased blood urea nitrogen (BUN), creatinine, and urinary proteins 1
  • Direct glomerular and tubular cell injury 1
  • Production of hydrogen peroxide (H2O2) when the two compounds were coincubated 1

• Critically, these toxic effects occurred ONLY when vitamin C and copper were used in combination—neither caused harm when used alone. 1

Clinical Implications

If You Must Supplement Both Minerals

• Separate the timing of administration significantly (ideally by several hours or take at different times of day) to prevent simultaneous presence in the gastrointestinal tract and bloodstream
• The interaction occurs both systemically and at the cellular level, so even with separated timing, some risk may remain 1

Dosing Considerations When Copper Supplementation is Necessary

For therapeutic copper replacement (not routine supplementation):

• Therapeutic doses range from 4-8 mg daily for copper deficiency myelopathy 3
• Standard supplementation provides only 1-3 mg copper daily 3
• Always maintain a zinc-to-copper ratio of 8-15 mg zinc per 1 mg copper when supplementing both minerals 3

Vitamin C Dosing Limits

• Vitamin C supplementation should be limited to ≤500 mg daily maximum when any copper supplementation is occurring 4
• Higher doses of vitamin C (>500 mg) enhance iron absorption and can mobilize metals from tissue stores, potentially worsening the pro-oxidant interaction with copper 4

Protective Strategies If Exposure Has Occurred

• N-acetylcysteine (NAC) completely prevented the oxidative damage and kidney injury caused by vitamin C plus copper combination 1
• Catalase also abolished the cellular damage in experimental models 1
• Vitamin E is generally protective against copper-induced oxidative damage 2

Common Clinical Pitfalls to Avoid

• Do not assume that because both are "natural" supplements, they are safe to combine—this is a dangerous misconception 1
• Do not use multivitamins containing both copper and high-dose vitamin C (>500 mg) 4
• Do not supplement copper without checking zinc levels first, as zinc-copper interactions are bidirectional and zinc excess is a common cause of copper deficiency 3
• Do not use standard supplementation doses (1-3 mg daily) to treat established copper deficiency—these are prophylactic doses only and therapeutic doses of 4-8 mg daily are required 3

Special Populations at Higher Risk

Patients requiring therapeutic copper replacement:

• Post-bariatric surgery patients 3
• Patients on continuous renal replacement therapy for >2 weeks 5
• Patients with copper deficiency myelopathy 3

In these populations, the risk of combining copper with vitamin C is even more critical to avoid, as they require higher copper doses that would amplify the Fenton reaction.

Monitoring Requirements

If copper supplementation is necessary:

• Measure plasma copper simultaneously with C-reactive protein (CRP), as inflammation falsely elevates copper levels 3
• Check both zinc and copper levels together before initiating copper replacement 3
• Monitor kidney function (BUN, creatinine) if inadvertent co-administration has occurred 1