Supplements that can lower blood sugar levels. A balanced diet is recommended while taking fenugreek supplements and it does not appear to be any specific foods or drinks one should avoid. However, it is important to avoid taking additional supplements that can lower blood sugar levels or thin the blood. These medications can interact with fenugreek and cause unwanted side effects. Supplements that can lower blood sugar levels. A balanced diet is recommended while taking fenugreek supplements and it does not appear to be any specific foods or drinks one should avoid. However, it is important to avoid taking additional supplements that can lower blood sugar levels or thin the blood. These medications can interact with fenugreek and cause unwanted side effects.