The safety of curcumin is demonstrated by the fact that it has been consumed for centuries at levels of up to 10 mg/day by people in certain countries. Curcumin was not toxic to humans in doses up to 8000 mg/day when taken by mouth for 3 months. Multiple other human trials have also found it to be safe with no alteration of liver or renal function tests.
Large doses of turmeric powder may cause gastrointestinal irritation in some persons and very high dosages have been shown to reduce fertility in male rats (human equivalent doses would be 35 g turmeric/70 kg adult). Normal therapeutic dosages of turmeric are not expected to affect fertility. Contact dermatitis has been reported, as has a single case of anaphylaxis.
Controlled studies are not available so interactions are based on evidence of activity and are largely theoretical and speculative.
Turmeric has a theoretical interaction with antiplatelet drugs; antiplatelet properties have been demonstrated for curcumin, therefore it may produce an additive effect.
The clinical significance of this interaction is unclear and likely to be dose-dependent.
Animal studies suggest curcumin may reduce drug efficacy — avoid.