I used to have exactly what you described with both my pregnancies...sometimes, to the point they would totally obscure my vision for a few seconds. Yes, definitely low blood pressure. Bending over or standing up fast will do that. Just do these things slowly & take all of the above advice.
In the thousands of cases we have treated we have not once seen any sort of coronary incident occur during or shortly after treatment. The same applies to cerebral vascular accidents. Nor have we ever seen a case of thrombosis of any sort develop during treatment, even though a high blood pressure is rapidly lowered. In this respect, too, the HCG treatment resembles pregnancy.
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I have high blood pressure, and am on meds myself for it (mild ones but nonetheless) when i am on HCG i have to go off completely, and even without my meds my BP hovers around 100/70 - right about the same as michael phelps' LOL
Yours may be lowering itself too. The others gave good advice, standing up slow, etc. It will right itself when you go off hcg.