So I eat two bowls of cereal with milk a day, live in Texas and out in the sun several times a week (mowing, gardening, etc). Do I need to worry about vitamin D?
Your primary care physician is who you should ask. Mine takes a blood test with the yearly physical, which includes a vitamin D measurement. They can tell if you're deficient and by how much.
If you're out in the sun every day, probably not. If you are indoors all day, it's probably a good idea to take a supplement. This calculator page is a great way to estimate how much time outside it would take for you to get generate a specific level of vitamin D given your skin colour, latitude, cloud conditions, time of day and so on:
For me it calculates only 15mins needed in the sun to get an equivalent dose of 1000IU. Note however that depending on where you read, a recommended dose per day may be 10,000-15,000IU.
Consider that your body evolved to be in the sun all day every day. It's possible you could still be D deficient even if you get a lot of sun relative to the typical sedentary person. A vitamin D panel can be purchased at most labs for $70. They usually offer packages that will run a complete blood count, chem, and others for a more economical price. You do not need a Dr's prescription to get these labs done. You can interpret the results yourself with a little bit of research before you go to the Dr.
I get my own labs done a few times a year so when I sit down with my doctor I can show them the labs in Apple Health and then it doesn't take 3 visits to have a real conversation. You are the only advocate in the health care system for your health. I encourage everyone to lean in when dealing with doctors. I make them explain everything including their rationale. You'll find many doctors disagree with each other on even the most common problems. If they don't have the time to sit with you and explain your health to you then they shouldn't be your doctor.
You need a blood test to know. If you're out in the sun that much though you're probably okay. But never trust the opinion of an online armchair doctor. The tests are relatively cheap if you get it with your annual exam which you should.
