I try and make sure I'm clean before I go see the doctor, especially if they're likely to want to put their hands on me. For example, my neurologist tends to lie me down, turn me over, tip me to the left, then to the right, check my reflexes etc - so I need clean hair so it will fall back into place when I can finally sit up straight.
If I'm seeing the doctor because I'm really ill, feeling ghastly - I tend to do without makeup. Maybe clear lip gloss if my lips are feeling chapped. But no colour - WYSIWYG. As you said, it can be misleading. I've had doctors tell me how well I look and not take me seriously, because I was wearing makeup.
If it's a checkup and I'm feeling awful, I will wear bright colours, usually red. Bright colours cheer me up. My previous GP worked out the pattern and would generally check my lymph glands if he saw me wearing a lot of red.
Today I was seeing the GP but also meeting mother in law. She's been critical of my diet, has been stressing loudly about how pale I look. If we're out and about together and someone says, "Wow, you've lost so much weight, you look great!" she HAS to add, "I think she's looking dreadfully pale, I don't like her colour." I'm sure people agree just to be polite - she then grabs onto this triumphantly and keeps reminding me that so-and-so agreed with her that I look pale, then I get ANOTHER lecture about my diet being too drastic.
So going to the doctor when mother in law is with me - I wear makeup, especially blusher. I also wear makeup when shopping with her. I also choose my clothes carefully - some colours brighten my face, others make me look sick. My current GP is a woman, so I'm not too concerned about makeup - she won't be misled if I'm a painted lady, unlike her male colleagues.
Because mother in law has been fretting about my very drastic diet, I've been making a point of worrying about my appearance a lot more than I would have. I keep my roots touched up (I do my own hair at home). I try to keep my hair styled in a way that looks OK (my hairdresser is a bit pot luck though). I wear as little makeup as I can get away with, but to NOT look sick, I know what I need to wear - eyeshadow at least, in a neutral dark plum shade in the eyelid crease, because it balances the plum-coloured dark shadows under my eyes and makes them less obvious; kohl eyeliner just outside the lash line, smudged slightly (thicker if it's evening); a dark red-brown lipstick in as long-lasting as I can get, because that shade also lifts the rest of my face. I tend to cheat and use the same lipstick as a blusher. I rarely wear foundation, but if I do I mix a liquid foundation in the palm of my hand, with a few drops of moisturiser.
My last long stint in hospital was about ten years ago. I was there for three weeks, mostly for a rest and for tests. I made a point of getting dressed every morning, wearing tracksuits or similar. I tidied my hair, did my nails and wore make-up. I wanted to make the point that I did not want to be illness-focussed.
If I'm seeing my eye doctor, I go without eye makeup. I might still wear plum eyeshadow in the eyelid crease, but nothing else.
At home and just round the place, I don't wear makeup. I'll wear lip gloss mainly to prevent chapped lips. Same with moisturiser - I slather it on mostly because my skin feels better if I do. After a shower or a swim at the beach I tend to pile on more body moisturiser, but what I use is not expensive - I often make my own skin treatments from various vegetable oils. I'm known to raid the olive oil from the kitchen, to slather on my legs and arms in summer. If I spill a bit of olive oil when cooking, I wipe it off onto my skin.
If I'm really crook and have called the ambulance, they get what they get - and it's usually not pretty. But it doesn't matter, I usually don't have my glasses on anyway, so I can't see a thing. I HAVE changed into my pyjamas to wait for the ambos, but only if what I was wearing was totally unacceptable. Don't ask.
I do travel with the bare minimum of make-up kits though. I can do my make-up with a couple of tools, the whole lot small enough to hide in the palm of my hand - one kohl pencil (propelling pencil type), one small lipstick compact and one small eyeshadow compact, each with mirror. When we went to New Zealand on holiday for three weeks, that was all the makeup I took for the entire time. Oh, I did have a spare lipstick, I needed that because I used one up while we were away. If I've made the choice to wear makeup, and I've eaten off my lipstick, I usually discreetly replace it as soon as I can. I can do it by feel, even in the dark.
Where it's no longer going to confuse a doctor about how I really am, I do tend to fuss a little more about my makeup because it gives me something else to think about. It also sends a message that I'm not illness-focussed - I've had too much contact with doctors who treat patients who ARE, I want to make it clear I'm not playing for sympathy.
I know this sounds contradictory - I guess for me the answer is complex.
Marg