"Is it risky to take resveratrol?"

Resveratrol is a natural product and even a too high dose will not have any toxic effects on your body.
However, there is a recommended dose of resveratrol:

Start with a lose dose and then increase it gradually:

Dosage of resveratrol (per day):
1. week: 100 mg
2. week: 500mg
4. week: 1000mg
7. week: 1500mg
10.+ week: 2000mg

As I said there are no side effects or even toxic effects if you your daily dose is too high. By increasing it gradually, you allow your body to get used to it slowly.

Does resveratrol have any side effects?

Though resveratrol has more than its share of health benefits, it also has some side effects. Resveratrol side effects and risks are usually mild, but they are still notable. Many people will tell you that this drug has absolutely no flaws, simply because they want to sell it to you. This article will uncover the truth about resveratrol side effects and risks that can’t be found elsewhere.

A “buzzed” feeling

A very common resveratrol side effect is a “buzzed” or hyper feeling. This is usually mild and generally goes away quickly, but many people have reported this. Many people also link this feeling to dizziness, which is also common among resveratrol consumers.
Stomach cramping and diarrhea
Like thousands of other drugs and natural supplements, resveratrol has been linked to stomach cramping and other stomach issues, such as diarrhea. Though generally mild and not lasting, this resveratrol side effect is worth mentioning because it is found very commonly. In fact, this is probably the #1 reported risk of resveratrol.

Insomnia

Insomnia is a rare resveratrol side effect, but it has been reported by several people. Most people who reported this said that it came on very quickly and lasted for seemingly random amounts of time. Some reported that they could not sleep for an hour or two, while others have reported whole days of sleeplessness.

Increased blood pressure

This one is extremely rare, but some people have reported increased blood pressure as a resveratrol side effect. Generally the raise was slight, and it often went down days or weeks later. Still, enough people reported this that it is worth a mention.