I have high blood pressure i have asthma can i take a decongestant for a cough expectorant?

Short term :yes : Yes for a short time you may take decongestants. Not recommended for an extended treatment. Treat underlying asthma with inhaled steroids, bronchodilators. See your doctor for any prolonged symptoms.

Best to ask doctor: what inhaler you need that will help reduce coughing and improve asthma. If you do need it for a cold or other reason, go for a expectorant without decongestant instead, so it won't affect your blood pressure. Check with your doctor first! For example, guaifenisin by itself is an expectorant, and will help reduce coughing by what it does in in the gut. However, not if you have cough from asthma.

Avoid D formulations: They have substances that will lead to rise in adrenaline or mimicking adrenaline which can lead to higher BP and heart rate. Simple Mucinex (guaifenesin) would work just fine