The most common side effects of saffron include nausea, changes in appetite, dry mouth, headache, anxiety, and drowsiness.[1] Changes in blood parameters have been reported in studies using doses of 60–400 mg daily, although it’s not clear if this has any clinical implications.[2][1] At excessively high doses (1,200–2,000 mg), saffron has been reported to cause vomiting, diarrhea, and bleeding.[3] Supplementing with isolated crocin (one of the active compounds in saffron) at normal doses may raise serum creatinine levels, which could indicate a risk of kidney damage.[4]
There are concerns regarding the quality of saffron supplements. Some of the important compounds in saffron are sensitive to light, oxygen, and temperature. Further, the way saffron is grown, harvested, and processed can alter its chemical composition. Due to its high economic value, saffron has also historically been prone to adulteration.[5] These factors may lead to large variations in the types and amounts of active compounds found in a saffron supplement which could impact its effectiveness. Choosing a supplement that is third-party tested can help ensure its quality.
Lastly, most of the research on saffron has been conducted in Iran, and its effects on other populations require further validation.