<p class="MsoNormal">A doctor's approval is required before taking <strong style="mso-bidi-font-weight: normal;">Viagra (sildenafil) twice day. The usual dose of Viagra is one pill once day, however it is also given as required. Overdosing on Viagra raises the chance of negative effects and may not improve erectile function any further than recommended. And if you use Viagra often enough without a doctor's supervision, you run the risk of developing a tolerance to the medicine and eventually becoming dependent on it to have an erection. Always with your physician before increasing the frequency of your Viagra dosage beyond once daily. They will be able to assess your condition, make any required adjustments to your treatment plan, and suggest other ways to deal with erectile dysfunction.