Small studies seem to suggest that even though Curcumin is a “natural” product, it may cause side effects. Curcumin has extensively been studied as a dietary supplement but not as a drug. Although this supplement has a very few side effects, most commonly reported are stomach upset, nausea and diarrhea, it is however important that we do not disregard this. Some of the common Curcumin side effects are discussed below. 

Gastrointestinal Problems
Curcumin may cause side effects that are mild in nature and may subside instantly -- nausea, upset stomach, and diarrhea. If high doses of Curcumin are taken for a long period of time, then some severe signs of gastrointestinal pain may occur because large amount Curcumin can increase the production of stomach acids and may cause heartburn and, of course, stomach ulcer. Some of this serious pain include excessive diarrhea, vomiting, dark, tarry stools, bloody stools, vomiting blood, etc.

Uncontrolled Bleeding
Curcumin has a tendency to slow down the process of blood clotting. As a result, those people who have bleeding disorders may experience harsh bleeding even from very small cuts and bruises. Curcumin also increases the probability of weighty bleeding during or after surgery. Thus, people who are going to surgery are advised to stop consuming Curcumin supplements at least two weeks before the scheduled surgery.

Liver and Gallbladder Problem
The liver and the gallbladder, two of the most significant organ of the digestive system, may be poisoned by excess intake of Curcumin. According to the Linus Pauling Institute at Oregon State University, it may cause the gallbladder to contract, sometimes called the gallbladder squeezing. Curcumin increases the flow of bile produced by the liver. It provokes the gallstone problem by washing out the gallstone out of the gallbladder and causes obstruction in the bile duct. It now results to a gallbladder attack and it happens due to increase in the flow of bile from the liver.
 
Allergies
A number of people tend to get allergic reaction when Curcumin is applied topically. Some of the allergic reactions are skin inflammation, irritation, burning sensation, and hives that usually occur within the first 24 to 72 hours of exposure to the allergen. Anaphylaxis, a serious allergic reaction is found to occur only in some rare cases after consumption of Curcumin.

Uterine Stimulation
 According to the National Institutes of Health, pregnant women should not use turmeric herbal supplements because of the fact that it can cause uterine simulation and can stimulate menstrual flow. As for now, no evidence has been established to point out that eating turmeric in foods causes abnormal fetal development. As recommended, pregnant women should consult with their physician before using turmeric Curcumin or any herbal supplement.
 
Decrease in Blood Sugar
 
According to the University of Maryland Medical Center, turmeric causes a lowering of blood sugar. People with hypoglycemia should discuss with their doctor before taking any turmeric supplements because it has been found that it could cause a significant blood sugar drop when combined with diabetic medications.
 
“A relatively high number of reports suggests that curcumin may cause toxicity under specific conditions. In 1976 Goodpasture and Arrighi found that turmeric caused a doseand time-dependent induction of chromosome aberrations in several mammalian cell lines; these alterations were observedat concentrations of 10 lg mL^-1. .¹Accumulating data have demonstrated since then that curcumin can induce DNA damage and chromosomal alterations both in vitro and in vivo at concentrations similar to those reported to exert beneficial effect.^2–10

For instance, curcumin concentrations of 2.5 and 5 lg mL¹ were shown to induce DNA damage to both the mitochondrial and nuclear genomes in cells.⁸ .These reports raise concern about curcumin safety, as the induction of DNA alterations is a common event in carcinogenesis.”
 
If you suspect that you are having Curcumin side effects, report immediately to your doctor so that they can take the next course of action to cure the problem. As what you have read, most of the Curmeric side effects occur primarily because of high dose of the supplement or to those who have pre-existing health conditions. In general, therefore, side effects of Curmeric extracts can be prevented if you talk to your doctor before starting the supplements.