Extrude a planar curve

When i select Curve from objects - extract an isocurve - then extend it - planar to a point - then extrude a curve where the extension starts - The extension goes the wrong way it folds back on itself
why is this.

Hello - presumably the curve is not planar - in that case the default extrusion direction is the CPlane normal - feel free to post a file with the curve.