Fiscal dominance in Iran has limited the independence of the central bank and made the monetary base dependent on government debt. This study aims to test the asymmetric effect of government debt on monetary base and to examine the moderating role of oil prices, unofficial exchange rates, and economic sanctions. This study uses seasonal data for the period 1991-2024 and employs a nonlinear distributed lag (NARDL) autoregressive model, and also uses the Zevet-Andrews unit root test to identify structural failures. The main innovation of the paper is defined at three levels: first, considering a dummy variable for periods of severe sanctions; second, adding an interaction term between government debt and low oil prices; and third, separating the effects of positive and negative government debt shocks. In this context, the bounds test confirms the existence of a stable long-run relationship. The long-run elasticity of the positive shock to government debt is 0.041, which is more than ten times the elasticity of the negative shock (0.0039). The interaction term between government debt and low oil prices increases the final coefficient to 0.068, indicating the intensification of fiscal dominance during periods of foreign exchange deficits. The dummy variable of severe sanctions also has a positive and direct effect on the monetary base. On the other hand, the consumer price index, with a long-run elasticity of 1.28, strengthens the vicious cycle of inflation-liquidity. Other findings show that fiscal dominance in Iran has violated the independence of the Central Bank by making the monetary base dependent on government debt. Therefore, the need to implement structural reforms, including a legal limit on borrowing to a maximum of two percent of oil revenues, designing a countercyclical fiscal rule based on oil prices, and establishing a currency stabilization fund to neutralize sanctions shocks, are recommended as basic prerequisites for controlling the monetary base.