From the Guidelines

Curcumin is generally considered safe.

The majority of studies suggest that curcumin is well tolerated without significant treatment-related side effects 1.
However, it may interact with coagulation and increase the risk of bleeding, particularly when used perioperatively 1.
Curcumin has been shown to prolong activated partial thromboplastin time and may exhibit antiplatelet effects 1.
Despite its potential benefits, curcumin has poor bioavailability, which may limit its effectiveness 1.

Patients taking curcumin should be aware of the potential risk of bleeding and monitor their coagulation parameters closely, especially when used in combination with other medications that affect coagulation 1.
The use of curcumin in patients with immune-mediated diseases may be beneficial due to its immunomodulating properties, but larger studies are needed to confirm its efficacy 1.
Clinicians should weigh the potential benefits of curcumin against the risks of delaying more effective therapy, particularly in patients with mild-to-moderate ulcerative colitis 1.

From the Research

Curcumin has been shown to be safe in several studies, with no toxicity reported at high doses (up to 12 g/day) in humans 2.
A phase 1 human trial with 25 subjects using up to 8000 mg of curcumin per day for 3 months found no toxicity from curcumin 3.
Five other human trials using 1125-2500 mg of curcumin per day have also found it to be safe 3.
Curcumin has been demonstrated to be safe in six human trials and has demonstrated anti-inflammatory activity 3.
However, excessive intake of curcumin may have adverse effects on the kidneys, heart, liver, blood, and immune system 4.

Curcumin exhibits poor bioavailability due to poor absorption, rapid metabolism, and rapid systemic elimination 2.
Despite the lower bioavailability, therapeutic efficacy of curcumin against various human diseases, including cancer, cardiovascular diseases, diabetes, arthritis, neurological diseases, and Crohn's disease, has been documented 2.
Curcumin has anti-inflammatory, antioxidant, antiproliferative, and antiangiogenic activities, making it a potential therapeutic agent for the treatment of various diseases 2, 5.
The anti-inflammatory effects of curcumin have been evaluated in several studies, and it has been shown to inhibit inflammatory cell proliferation, invasion, and angiogenesis through multiple molecular targets and mechanisms of action 5.

The clinical transformation of curcumin is not successful, and excessive intake of curcumin may have adverse effects on the kidneys, heart, liver, blood, and immune system 4.
The controversy surrounding the association between curcumin purity and effect is a limitation of its use as a therapeutic agent 4.
The low solubility of curcumin, leading to poor bioavailability, is a major limitation of its use as a therapeutic agent 4, 6.