I recently started thinking I am deficient in magnesium after dealing with a charlie horse during a 5K. I took out a book from my library called The Magnesium Miracle by Carolyn Dean M.D. which attributes so many conditions to a chronic magnesium deficiency brought on by industrialized farming and water treatment, etc. After 2 weeks of supplementing with magnesium oil and a multi-mineral supplement, my muscle cramps have lessened considerably, heart palpitations are gone, headaches are less frequent, and my energy is much improved. Sleep is better as well. For low blood pressure I checked to see what Dr. Dean recommends and she mentioned upping magnesium slowly, making sure other minerals are also being supplied, sea salt is being used and that plenty of water is being taken. I hope you find some of this helpful!
How critical is magnesium?
I love that book. I think I’ve bought about 10 copies over the years because I keep giving it to people. That book really helped me out several years ago. I had restless legs, anxiety, and suddenly developed heart palpitations. I went to the doctor, but at the time he said that heart palpitations happen, but if they get annoying he could put me on medication. (The palpitations had, of course, stopped by the time I arrived for my appointment.)
I went home, searched the web and learned about magnesium deficiency. I bought Carolyn Dean’s book and started supplementing with magnesium. Within a few days the restless legs and the heart palpitations were gone. The anxiety took longer, a little over a week.
It’s been a while since I read it, and I “loaned” my last copy so I can’t look it up, but she does mention a way to measure one’s magnesium levels the correct way to see if one is deficient. If I recall, a simple blood test may not provide an accurate picture. I would highly recommend reading that book. It may put your mind at ease or arm you with more knowledge to discuss with your doctor or pharmacist.
Then why supplement? 
I track in Fitday which summarizes the vitamins and minerals consumed in the food I eat. I use it as a guide and supplement accordingly.
Sue777, just wondering, did you actually pursue the potassium (Lite Salt) and are you feeling better? I assume you left the magnesium on the shelf for now.
Cautions
Serum or plasma magnesium concentration provides only an approximate guide to the presence or absence of magnesium deficiency. Hypomagnesemia reliably indicates magnesium deficiency, but its absence does not exclude significant magnesium depletion. The concentration of magnesium in serum has not been shown to correlate with any other tissue pools of magnesium except interstitial fluid.
Serum totalmagnesium can be normal in the
presence of intracellular depletion.
Thus, among patients at risk for
magnesium deficiency, oral
supplementation of magnesium may
be warranted, even if serum (total)
magnesium concentration is within the
normal range. Renal impairment is a
common relative contraindication
https://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/8448
Hi Karen. Yes, I have Salt Lite and use it probably every other day. Don’t know how much I need to supplement and I know it’s dangerous to get too much potassium so I go easy with it. And yes, I’m having no more low blood pressure episodes. Thanks for asking. 
Hi Virginia,
Which type of magnesium did you choose to supplement with and what doesage?
Thanks!
Hi Kelly,
I use magnesium glycinate because that is supposedly the most bio available. I do think that’s true because when I take the other forms I have loose you-know-whats.
I take anywhere from 400 to 600 mg a day. I try to break up the dosage over the course of the day but don’t always remember. Taking it all at once in the evening seems to work fine.
I also take calcium each day since I can’t eat dairy.