Health workforce projections support needs-aligned and geographically equitable care by anticipating service demand, workforce supply, and regional gaps. We develop two indicators: the replacement requirement, measuring capacity needed to offset demand and workforce exits, and the projected supply ratio, assessing provision under workforce-entry scenarios. We project general practitioner (GP) care in Lower Saxony, Germany, across 105 planning areas from 2025 to 2040. By 2040, the cumulative GP replacement requirement needed to maintain the 2025 supply ratio ranges from about 50% to more than 90% of baseline capacity across planning areas and is concentrated in the next decade. Under the baseline scenario, 4,872 GP full-time equivalents (FTEs) remain in 2040 against a requirement of 5,131. The number of planning areas with a supply ratio below 75% rises from two in 2025 to 16 in 2040. Securing GP care is therefore primarily a challenge of allocation, requiring education and recruitment policies to be combined with targeted measures to improve overall supply.