NO do not take this without asking your doctor and heres some more info! Before using NyQuil Liquid:
Some medical conditions may interact with NyQuil Liquid. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

if you are pregnant, plan to become pregnant, or are breast-feeding
if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
if you have allergies to medicines, foods, or other substances
if you have a fast, slow, or irregular heartbeat
if you have a history of adrenal gland problems (eg, adrenal gland tumor); heart problems; high blood pressure; diabetes; heart blood vessel problems; stroke; glaucoma; a blockage of your bladder, stomach, or intestines; ulcers; trouble urinating; an enlarged prostate or other prostate problems; seizures; an overactive thyroid; liver problems; or if you consume more than 3 alcohol-containing drinks per day
if you have a history of asthma, chronic cough, lung problems (eg, chronic bronchitis, emphysema), or chronic obstructive pulmonary disease (COPD), or if cough occurs with large amounts of mucus
Some MEDICINES MAY INTERACT with NyQuil Liquid. Tell your health care provider if you are taking any other medicines, especially any of the following:

Beta-blockers (eg, propranolol), COMT inhibitors (eg, tolcapone), furazolidone, indomethacin, isoniazid, MAO inhibitors (eg, phenelzine), sodium oxybate (GHB), or tricyclic antidepressants (eg, amitriptyline) because side effects of NyQuil Liquid may be increased
Anticoagulants (eg, warfarin), digoxin, or droxidopa because risk of bleeding, irregular heartbeat or heart attack may be increased
Bromocriptine or hydantoins (eg, phenytoin) because side effects may be increased by NyQuil Liquid
Guanadrel, guanethidine, mecamylamine, methyldopa, or reserpine because effectiveness may be decreased by NyQuil Liquid
This may not be a complete list of all interactions that may occur. Ask your health care provider if NyQuil Liquid may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

NyQuil is safe to use when you are hypertensive or diabetic. However, it is possible that it will interact with some of the medication you are taking.

I would say No. I went to bed with bad sore throat lots of mucous coughing,took nyquil. The next moring I was so sleepy, had a hard time waking up 1pm , draged my self out of bed went to Dr thinking I'm sure I have a sinus infection. Now the back of neck is hurting at the base of the skull, and my forehead. the Nurse takes my blood pressure its 200/90, she says its the cuff its broke, she goes and comes back to do it 4 more times. From 1:30 to 5: it drops 10 points. No one seems very concerned. I'm thinking I could have had a stroke, if it went higher. Soon as I returened home I took blood pressure pills. This makes me think I should not take Nyquil. What do you think?

As of now I'd say no. But only because we know so little about your situation, and with such little information we'd never be able to say one way or another correctly. You should check with your doctor about taking Nyquil with your situation. On paper it may not look so bad, but your situation may not warrant its use.