Haven'y experienced this myself but here's some information I found:-
"Stomach upset is the second most common complaint I hear from tea drinkers after caffeine intolerance.
The culprits? Caffeine and polyphenols. They cause indigestion by stimulating the production of gastric acid.
Indigestion is often described as a feeling of fullness, bloating, nausea or gassy discomfort in the chest or abdomen. The symptoms develop during meals or shortly afterwards.
Tea can also be a problem for those prone to heartburn and stomach ulcer. Heartburn results when gastric acids rise up and spill into the oesophagus causing irritation.
Here are some tips on how to deal with green tea and stomach gastric irritation.
Tea is not the only food that causes the stomach to produce acids. Beverages such as coffee, caffeine or carbonated beverages and alcohol have the same effect.
Watch out for foods such as raw onions, garlic, black pepper, chili, vinegar, spicy foods, cloves, nutmeg and all fatty foods such as dairy. They, too, irritate the stomach.
Avoid cooking food with fat or oil. Boil. Broil. Bake. Grill. Poach. Steam. Avoid frying.
Avoid a large meal that completely fills the stomach. Eat slowly. Chew thoroughly.
If you drink loose tea, brew it half-strength. Add not more than 2 to 3 grams of leaves per cup. Full-strength tea causes the stomach to secret more acid.
Drink tea in between meals. Avoid drinking tea with a meal or half an hour afterwards.
Avoid drinking tea with an empty stomach.
Drink tea with some ginger. Some people have found it soothes the stomach.
Add milk and sugar. A 1984 study found that milk and sugar reduce gastric acid production.
If you add milk, try using soya milk. A recent study about tea with milk found that animal milk contains casein that binds to catechins (the stuff that contains most of the tea antioxidants), reducing their effectiveness.
Soya milk contains lecithin that has a different molecular structure to casein, and so is unlikely to bind to tea catechins the way casein does.
Try drinking a darker oolong tea (such as the Wuyi Rock tea) or an aged oolong or pu-erh tea. They tend to be gentler on the stomach. Alternatively, go herbal."
Hello you! I take the Green Tea Pill but have never had the nausea, however I always make sure I take them AFTER breakfast / a meal. If you're taking any pills on an empty stomach they can make you feel a bit sickly, even if you're having food afterwards. The funny thing is, my pills say to take them after food rather than before - it's the same for my Cod Liver Oil and Multi Vits. Perhaps try taking them after you've had food for a couple of days and see if this helps at all :-) My Green Tea pills also say that you can split them open and make them into a tea rather than take them as a pill - if you can do this with yours you should give it a try because they might be less potent if they are diluted a bit. Hope this helps, let me know how you get on because I take them myself so it would be interesting to find out!