Valium has side effects which are similar to the ones with other benzodiazepines. Most commonly occurred ones are: headache, blurred vision, fatigue. Any allergic reactions symptoms are less common, but they can include heavy breathing, skin rash and etc. More serious conditions, such as vomiting, stomachache, fever, have to be reported to your doctor immediately in order to avoid any further complications.
Seek immediate medical attention if any of the reasons you started taking Valium for worsened during the treatment process. Keep in mind that your body may develop tolerance towards the drug in case you have been using it for a long time. Advice with a physician in regards to adjustment of suggested dose of intake in order to receive most benefits out of the Diazepam.