I'm taking 500mg and it barely brought it up to 1.9. I'd hate to see it without being on it. But it helped with my legs. I still cramp up in a car uber bad but Charlie Horses are better. Thankfully.

Magnesium IS a blood test (or urine test) depending on looking at kidney or uncontrollable diabetes, but no I've never has on my list of problems

It's not found in the blood but in the bone. So id have to have to have some kind of biopsy or something. Sounds scary. But I have migraines, hypoglycemia, I have lost my appetite, my balance is horrible, I get infections, my immune system is almost nonexistent, I have nerve twitching, muscle spasms and cramps, lethargy, anxiety, impaired memory, irregular heart rhythm, insomnia, nausea, depression, muscle weakness, chronic fatigue, vertigo, difficulty swallowing, and chest pain.

And these are just the basic ones too...

I take supplements to help with cramps but not that I'm aware of. I've heard it helps. Have you taken a blood test?