Lead exposure: how long to wait to get blood test?

If someone has been exposed to a significant amount of lead (inhalation or ingestion over one day or week,) how long should they wait to get a blood test in order to ensure that the testing accurately reflects the total lead burden in the body?
Would testing too soon cause a false negative because some lead has not been absorbed into the bloodstream yet?

The first question to ask would be: “What makes said person think they have been exposed to a significant amount of Lead?”

If I thought I got a good dose of lead (ie spent the day in a dusty house and didn’t realize the dust was lead paint being sanded), I’d call my county’s health department and ask them for advice. They could likely give me some info and point me to the best hospital in the area to handle this type of thing. You’re regular doctor could probably do the same thing.
As far as waiting, lead has been a problem for so long that I would assume there’s a protocol for this. Without knowing it, it seems trivial to get tested right away. If it’s positive, start treatment, if it’s negative, wait a few weeks and get tested again.

A little bit of checking on wiki, shows that bloodwork can show how much lead is in your blood. Levels of erythrocyte protoporphyrin in the blood will spike a few weeks after lead exposure.
I’d assume a test for lead soon after exposure and a test for erythrocyte protoporphyrin (and maybe lead as well) a few weeks later would be a good course of action.

But again, your family doctor, a local hospital or your city/county health department would be who I’d talk to first.

Interesting, why would there be a dual test for erthrocyn protoporhyn (unless it’s to hedge against the lead turning up a false negative?)

I’d have to look it up. Classically, people were exposed to lead through plumbing, petrol, industrial exposures, glass and tableware. Most of these exposures are chronic (as opposed to acute) and so a minimum time frame probably doesn’t apply; it is already there. Acute exposures probably depend on the dose and route of ingestion, so the ideal time would vary. Of course, there is no reason you could not test more than once.

In addition to lead levels, I vaguely recall from medical school that exposures cause basophilic stippling in leukocytes.

That makes sense. From what I heard, if inhaled, lead essentially goes into the bloodstream immediately, but if ingested, it can take several days to show up.