Assuming you do not have a genetic disease which inhibits the absorption of iron, take more than you are. Low iron is incredibly obvious in our bodies. I take several supplements because I am dificient, but none of them create an obvious noticeable change like when my iron gets into normal ranges. I take minimum 2 slowfe’s a day (Slowfe is an over the counter iron cupplement, I only take the brand not the generic) the iron is absorbed best on an empty stomach, orange juice is good with it also because vitamin c and the acid helps it absorb. But, some people feel queasy if they take iron alone. Iron brings oxygen to the muscle, and your muscles are working with less. The other vitamins to check are vitamin D and B12. Do not assume your doctor checked those many don’t.
Additionally, you must make sure your doctor checked your thyroid. At minimum did a TSH blood test (thyroid stimulating hormone). My muscles tire incredibly fast, and I am left weak and shaky, and my thyroid affects it a lot, besides the iron. If your TSH is over 4 it could explain some of your symptoms. The labs normal range is up to 5.5 most likely, but most endocrinologists feel above 4 is a slow thyroid. When mine is 5 I need 10 hours of sleep, I get a charlie horse in my bicep just from holding my phone for a few minutes to my ear. If I garden for an hour my hands are so shaky I can barely hold a glass, but then I recover within an hour and am steady again. It affects every muscle in my body. If I do my zumba full force, I feel like my legs might buckle beneath me afterwards. When my TSH is between 2–3 many of my symptoms are significantly better, the difference is drastic.
Other symptoms for slow thyroid are dry skin, dry eyes, hair falling out excessively, dry hair, needing more sleep, slow heart rate, high blood pressure, spacy or dizzy feeling. You may not have all symptoms.
Also, a fast thyroid, which would be your TSH is low, can also cause the muscle problems. Symptoms would be trouble sleeping or needing less sleep (but you still might get tired during the day) dry eyes, dry skin, dry hair and hair falling out, fast heart rate, pounding heart, abnormal blood pressure, spacey or dizzy feeling.
Do not assume your doctor checked your TSH, also regular GP’s will not necessarily treat or mention if your TSH was 5 since it falls in the labs normals range, but that is high. There has been discussion among the powers at be that the nornal range should be changed. Several years ago the vitamin D range was changed.
Hope you feel better.