Calcium
Calcium carbonate, Calcium citrate, Calcium gluconate, Calcium lactate, Caltrate, Calcium + vitamin D, Calcium-D3 Nycomed, Calcium Sandoz
Forms: Salts: carbonate, citrate, gluconate, lactate; often sold combined with vitamin D.
Essential mineral for bones, muscle contraction and nerves. Taken at the same time, calcium supplements cut absorption of iron and of levothyroxine.
Legal status: Sold freely as a supplement; calcium salts are also licensed medicines for deficiency and osteoporosis; not prohibited in sport.
What it gives
What people use it for and what the sources report. Strength is a general category from the literature: mild, clear or strong.
Purpose
Taken to cover low dietary intake and support bone health, mainly by athletes who avoid dairy, eat too little or have missing periods; the IOC lists it among nutrients athletes may need. It does not build muscle or strength and is not a routine add-on to steroids.
What people seek and what studies show
In 5,201 female navy recruits, calcium with vitamin D lowered stress fractures by about 20% during basic training. In adults over 50, a BMJ review rated the evidence that calcium supplements prevent fractures as weak and inconsistent, with no effect in the trials at lowest risk of bias. No effect on muscle or strength is known.
Effects
Evidence: Approved medicine — studied in people for its medical use
Sought effects by goal (as reported)
Possible side effects
Possible does not mean certain: whether they appear depends on dose, duration, individual response and monitoring. Below — what to watch for and how to notice it early.
2 possible side effects
level · how often it is reportedWhat the levels mean
Level: general category from the literature, not your personal risk
How often
- common
- reported often
- possible
- reported in some people
- rare
- reported occasionally
How to lower the risks
For 2 of 2 possible side effects there are specific ways to lower the chance: everyday measures, supplements and options a doctor may consider. No measure removes a risk completely.
Drink enough water, control blood pressure, avoid regular painkillers (NSAIDs).
How each option helps (3)
- Fluid & electrolyte management — Good hydration eases kidney stress from heavy training and heat; dehydration plus NSAIDs is a classic cause of acute kidney injury.
- Regular blood tests — Creatinine reads high in muscular people and with creatine; cystatin C and a urine test give a truer picture of the kidneys.
- Working with a doctor — Investigates protein in the urine or falling kidney function and can start treatment that slows kidney damage.
Low-level side effects
How each option helps (2)
- Working with a doctor — Assesses persistent vomiting or severe belly pain (possible pancreatitis or gallstones) and adjusts prescribed GLP-1 treatment when nausea persists.
- Pancreatin + dimeticone (Pankreoflat) — May ease heaviness and gas after meals; can cause nausea or diarrhea. Not for pork or cow's milk protein allergy (anaphylaxis reported) or early acute pancreatitis.
Check-ups and blood tests
Which tests and check-ups to do and when. This is a guide — agree the exact schedule with your doctor.
Which doctors can help
Get medical help at once if
- Much less urine than usual, cola-colored urine, new swelling, flank pain — see a doctor now.
In an emergency, call your local emergency number.
For women
Female athletes who eat too little or have missing periods are at higher risk of poor bone health; the IOC names calcium together with vitamin D for this group.
Myth & fact
“The more calcium, the stronger the bones.”
Not beyond what you need. In adults over 50, calcium from food was not linked to fracture risk and supplement trials show weak, inconsistent effects, while kidney stones and gut complaints became more common. A possible link to heart attacks is debated.
Combinations
Thiazides make the kidneys hold on to calcium, so calcium from supplements is excreted less and blood calcium can climb: thirst, nausea, constipation, confusion and strain on the kidneys. A calcium test shows it.
HydrochlorothiazideLarge amounts of calcium together with an absorbable alkali such as baking soda can cause calcium-alkali (milk-alkali) syndrome: high blood calcium, alkaline blood and kidney injury. Nausea, vomiting, unusual thirst, confusion or muscle weakness are reasons for a blood test.
Sodium bicarbonateSources
Possible side effects by body system, combinations, how to lower the risks and which tests to do — free.
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