That is a tricky issue. Even if your vitamins are made in the US from a reputable manufacturer, how do you know where the raw materials come from? China makes more than 90% of the ascorbic acid (vitamin C) that is used in supplements.
Fortunately, simple molecules can be analyzed to check what is in them. That’s what, for example, the USP seal stands for. Although the FDA does not regulate supplements and there is no guarantee as to any medical claims, a USP sign means that the manufacturer agreed for independent testing of the product and that the prosuct does not contain harmful impurities and that the label on the bottle lists the ingredients and their potency correctly.
http://www.usp.org/verification-services/verified-mark
I always check for this sign.
https://healthyeating.sfgate.com/vitamins-usp-seal-approval-10203.html
There are other independent testers:
Thank you!
@sabaray - I am not too familiar with CoQ10 formulations and what the poster meant by water and fat-soluble. The molecule itself is fat-soluble… Have to dig a little more. But you bet, formulations are important and make a difference for absorbtion and activity.
I’ve been taking multi-vitamins, D3, & Lutein for my eyes for years. Had my Vit D tested and I was extremely low.
I started taking glucosamine chondroitin with msm for a bum knee in January and it’s like new again! So nice to be able to walk limp free!
OK, looked a little at coQ10 formulation issues. Apparently, this fat-soluble substance is rock-solid in its pure form. Taking it as a solid does no good as it simply does not get absorbed (like a rock). Some manufacturers pulverize it finely with some hydrophobic and hydrophilic carriers, and that apparently helps with absorption in the GI tract. While the molecule itself has not been made any more water-soluble, such emulsions, dispersions, etc. help with getting it taken up. I would check the inactive ingredients carefully to make sure there is nothing that can be an issue.
Quinine, the active ingredient in tonic water, is useful for leg cramps. We used to give it in pill form in the hospital, but have since stopped as quinine has been found to prolong part of the EKG that can lead to a fatal heart rhythm. So if you take cardiac meds, or have heart rhythm issues, beware. I might be just silly, but I get leg cramps if I don’t have my daily banana which contains potassium. I take magnesium supplements.
coQ10 was recommended to me as useful for anyone with vascuar issues, which includes high blood pressure. I have since been able to get off the meds, but take the supplement regardless, as I fear the blood pressure problem returning.
The curcumin for joint pain/arthritis relief seems to have been helpful.
After a yearly Vit D test, my Dr. settled on 3000 units per day to keep my blood levels within norms. Due to lack of sun exposure in northern latitudes, bone density tends to decrease every winter, and summer gains don’t keep up with winter losses.
However, my mother, living in Arizona, but diagnosed with osteoporosis was taking 5000 units of Vit D daily, and lab work was normal. Then something went haywire at age 93, her Vit D levels zoomed to toxic levels, elevating her calcium levels and she was hospitalized. Vit D being fat soluble, sticks around for a very long time.
Vit C 500mg, Vit D (D3) 1000 IU daily.
Last year I developed a strange itchy rash that absolutely drove me nuts. Because I already have sensitive skin, I thought it was something in my environment, or laundry detergent, and I even considered scabies as I work in a school setting. After 3 Dr. visits, various rounds of steroids, and other troubleshooting methods including a skin biopsy…I had scurvy! Yes, scurvy! Evidently, my strict diet (I’ve lost over 100 lbs and have kept it off for 3years), caused me to develop a vitamin C deficiency. So I most definitely take a yucky, humongous strong multivitamin every day without fail. And I hate taking meds/pills, but my body definitely needs vitamins, especially since I eat so little.
@4MyKidz what did you (not) eat to get scurvy??
I’d think losing so much weight would mean you were eating more than the usual American number of fruits and veg. I’d expect someone with scurvy to be eating McDonalds hamburgers and cheese doodles all day long! 
What kind of strict weight loss diet does not include enough fruits and vegetables that contain vitamin C?
Or are all of the fruits and vegetables cooked enough to destroy their vitamin C?
Good questions @surfcity & @ucbalumnus ! I had this complete answer typed up, then hit save comment and it was just gone. 1st time that’s happened. Anywhoo, I follow a low carb, high protein diet and have been for the past 3 1/2years, which has helped me lose and keep off 100 lbs. Fruit tends to have more carbs than I need. At meals, I eat protein first, then veggies if I’m still hungry. I do not like salad. Most the time, I’m not hungry enough to eat a good portion of veggies. My snacks tend to be nuts, 1/2 banana, quest protein bars or low carb protein shakes. Like anything else, over time you condition yourslef to eat only certain things because you are so successful. Per my nutritionist and endo, who are happy that my weight is in the “normal” bmi range and not the “morbidly obese”range…I just need to diversify my diet (like eat a small orange!) and take a nasty multivitamin which I am working on. Hope that explains it 
If you don’t want to take vitamin D supplements, or drink lots of OJ, you can try rose hip tea or green chile salsa.
I have a jar of Hatch green chile salsa that has 120% RDA of Vitamin C in just 2 tablespoons (only 10 calories and 3 grams of carbs). Put that on your meat!
It also has 6% Vitamin A and 2% Iron.
@greenwitch Good idea about the green salsa! I’ll give it a try
Low calorie vegetables tend to be on the “good” lists of both low carb and low fat diets, and almost every other diet that tries or claims to be healthy.
Since @4MyKidz has a low whole foods diet, the vitamin deficiency makes sense. I won’t judge what works for her especially since I never struggled with obesity. I have gravitated to Vit D only to adding NAD+, cat’s claw, and ashwagandha for brain health as dementia is my families illness. But the cornerstone of the plan is opposite of @4MyKidz. A low sugar plant based diet with protein “on the side.”
Yep @GTalum , the most important thing is to find what works for you and stick with it. I’ve come across folks who think their diet is “The One” and then others try to jump on the bandwagon hoping it works for them. And I’ve come across the professional dieter who thinks he/she knows it all. And I’ve come across folks who ask how I lost & kept off all the weight but then their eyes glaze over when I describe my lifestyle. I just do what my medical team tells me to the best of my ability and adjust when necessary. It is definitely personal.
Boy did I get a lecture re Vit D from my internist. I live in a northern climate and with all the talk lately about the dangers of low vitamin D I decided to start taking a supplement. Having zero idea what my current levels were, for about 6 - 9 months I added 5000 IU of liquid Vit D to my every other morning yogurt. At my last doctor visit I asked to have my D checked. The results came back not toxic, but high at 67.
With doses offered from 500 to 50,000, it never occurred to me that 1000 might be too high a number for me.
I think if you are deficient in Vitamin D the supplements can make a huge difference in how you feel physically but always a good idea to get tested before you self-dose. I agree, it is confusing. My doctor told me a range of 40 to 60 was best and after 6 weeks of 50,000 units a week followed by 4000 a day, I was finally at 40. Hopefully I’ll maintain that!
My doctor told me to take 2000 units of D3 a day. The bottle suggests 1000 units. @Kajon did the bottle or package indicate a suggested dose? I can’t believe your doc did not give you a dosage.
My mom was just Dx with osteopenia. In reading some of the literature her doc gave her, it looks like Vitamin D is important for preventing this too.
@4MyKidz - good for you for keeping the weight off. My cholesterol has just started to creep up, so I need to go to a more plant based diet however. DH has been fond of the paleo diet and in concept I do agree that high carb (simple carbs) are not good for weight nor for heart health.
We are toying with going vegetarian 5 or 6 days a week. We both love salmon and fish so that is definitely a protein we will maintain