first of all.. if you are above 50, the blood pressure BP is within the normal range on the upper limits.. the 143mmHg is called the systolic pressure (the high pressure that the heart produces when it pumps the blood out) and the 87mmHg is called the diastolic pressure (or the resting pressure when the heart is resting for a brief moment); and as you get older, the normal range shifts upwards.. so 143/87mmHg can be an emergency in children, concerning in young adults but normal in older people..
however if the BP is above 180mmHg systolic and/or if it is above 120mmHg diastolic, then you need to see a doctor ASAP..
second.. whenever we check the BP, the subject must not be under physical and/or mental stress.. in fact when doctors and nurses mention the BP, they often mention "at rest"..
150/110mmHg at rest can be an emergency but 150/110mmHg while running a marathon can be perfectly normal..
the BP rises if you have just jumped a flight of stairs, if watched something upsetting, exciting or sad on the TV, or if the weather is hot and suffocating..
ideally, the subject would be asked to sit in a quiet and slightly chilled room for 20 minutes without phones, TV, magazines, or anything upsetting, before measuring the BP.. and if the BP was recorded high, you need to measure the BP 12 hours later to see if the numbers are consistent..
and finally, whenever the BP is quoted, you also need to know the PR - the pulse rate or the heart rate.. the PR should give some context to the BP reading.. if both the BP and HR are high, the subject may not be at rest; and the subject would be asked to sit for 20 minutes before measuring the BP again..
all the best..