hello welcome to hcm you have provided no information about which anti-hypertensive drugs your husband is taking,as there are large number of drugs available for hypertension and various drugs act via different mechanisms and cause different potential complications so kindly provide detailed information regarding treatment history of your husband so that we can evaluate and advice you regarding which appropriate drugs and treatment options would be best suitable for your husband... as far as dangerous low bp numbers are concerned,there is no such clear cut values and every individuals body reacts differently to any particular values of blood pressure,whats normal values for you might be low blood pressure for another individual and vice-versa...still,to give you a rough idea if the upper value of blood pressure ( systolic bp ) is below 90 and lower value ( diastolic bp ) is below 50 then you need to move to the ER urgently...there is a a very effective home procedure in case of a very low bp and if now medical aid is available nearby and im sure you will find it extremely useful information -- if blood pressure is at very low levels perform these 2 simple things and blood pressure will return back to normal levels (1) MAKE THE PERSON TO LIE DOWN ON A FLAT SURFACE AND RAISE BOTH HIS LEGS TO AN ANGLE OF 45-60 DEGREES ABOVE THE GROUND KEEPING THE LEGS STRAIGHT AS IT WILL MOVE THE VENOUS BLOOD OF LEGS RAPIDLY TOWARDS HEART AND THE COMPENSATORY PHYSIOLOGICAL MECHANISMS OF THE BODY WILL ALMOST IMMEDIETLY BRING THE BP LEVELS BACK TO THE NORMAL (2) GIVE 3-4 GLASS OF WATER MAKING SURE TO ADD AROUND 1/2 TABLESPOON OF TABLE SALT AND LEMON IN IT hope you find the above information to be very helpful regards hcm