ldj1002,
both the headaches and blood pressure drops with Tymlos are because of vasodilation. You can mitigate both effects by hydrating before the injection and having something salty. The effect begins quickly after the injection, really withing a minute. If you already have low blood pressure, you may notice loss of balance or lightheadedness. It is good to plan light safe activities for the first four hours after injection. You may not notice anything at all. Some people do take the shot at bedtime, especially if it makes them unsteady.
Tymlos is a really good choice